Lubricant base oil and method for producing same

ABSTRACT

A lubricant base oil that is a hydrocarbon oil that satisfies any of the following conditions (i), (ii) and (iii):
         (i) a hydrocarbon oil having a kinematic viscosity at 100° C. of 3.0 to 5.0 mm 2 /s, a viscosity index of 145 or more, and an SBV viscosity at −20° C. of 3,000 to 60,000 mPa·s,   (ii) a hydrocarbon oil having a kinematic viscosity at 100° C. of 5 to 9 mm 2 /s, a viscosity index of 155 or more, and an SBV viscosity at −20° C. of 3,000 to 30,000 mPa·s, and   (iii) a hydrocarbon oil having a kinematic viscosity at 100° C. of 2.0 to 3.0 mm 2 /s, a viscosity index of 130 or more, and an SBV viscosity at −30° C. of 1,000 to 30,000 mPa·s.

TECHNICAL FIELD

The present invention relates to a lubricant base oil and a method forproducing the same.

BACKGROUND ART

Conventionally, regarding a lubricant base oil and a lubricant oilcomposition, satisfaction of both a high viscosity index and alow-temperature viscosity characteristic has been attempted.

For example, by blending an additive agent such as a pour-pointdepressant into a lubricant base oil such as a highly-refined mineraloil, improvement of a low-temperature viscosity characteristic of alubricant oil has been attempted (for example, refer to PatentLiterature 1 to 3). Moreover, as a producing method of a high viscosityindex base oil, for feedstock containing natural and synthetic normalparaffins, a method of refining a lubricant base oil byhydrocracking/hydroisomerization is known (for example, refer to PatentLiterature 4 to 6).

A pour point is generally as an evaluation index of a low-temperatureviscosity characteristic of a lubricant base oil and a lubricant oil. Inaddition, a technique for evaluating a low-temperature viscositycharacteristic based on a lubricant base oil such as the content ofnormal paraffins and isoparaffins is also known.

CITATION LIST Patent Literature

Patent Literature 1: JP-A-04-036391

Patent Literature 2: JP-A-04-068082

Patent Literature 3: JP-A-04-120193

Patent Literature 4: JP-A-2005-154760

Patent Literature 5: JP-T-2006-502298

Patent Literature 6: JP-T-2002-503754

SUMMARY OF INVENTION Technical Problem

As described above, in general, it is considered that lower cold flowproperty of a lubricant base oil is better, and according to the studyof the present inventors, a conventional lubricant base oil having coldflow property has a problem in a sealing property. More specifically, alow viscosity of a lubricant base oil or, moreover, contraction of asealing material widens a gap, and when a pressure is applied to thesite, oil leakage becomes easy to occur.

The present invention has been made in view of these circumstances, andit is an object of the present invention to provide a lubricant base oilcapable of satisfying both a low-temperature viscosity characteristicand a sealing property at a high level, and a method for producing same.

Solution to Problem

In order to achieve the above-described object, firstly, the presentinventors attempted satisfaction of both a low-temperature viscositycharacteristic and a sealing property of a lubricant base oil using anSBV viscosity as an index, as an approach different from improvement ina low-temperature viscosity characteristic of a lubricant base oil usinga pour point as an index. As a result, it was found that when thekinematic viscosity at 100° C., viscosity index, and SBV viscosity at−20° C. of a lubricant base oil satisfy their respective specificrequirements, a sealing property can be improved while sufficientlymaintaining a low-temperature viscosity characteristic to complete thepresent invention.

That is, the present invention provides a lubricant base oil describedin the following [1] to [12], and a method for producing a lubricantbase oil described in the following [13] to [18].

[1] A lubricant base oil that is a hydrocarbon oil that satisfies any ofthe following conditions (i), (ii) and (iii):

(i) a hydrocarbon oil having a kinematic viscosity at 100° C. of 3.0 to5.0 mm²/s, a viscosity index of 145 or more, and an SBV viscosity at−20° C. of 3,000 to 60,000 mPa·s,

(ii) a hydrocarbon oil having a kinematic viscosity at 100° C. of 5 to 9mm²/s, a viscosity index of 155 or more, and an SBV viscosity at −20° C.of 3,000 to 30,000 mPa·s, and

(iii) a hydrocarbon oil having a kinematic viscosity at 100° C. of 2.0to 3.0 mm²/s, a viscosity index of 130 or more, and an SBV viscosity at−30° C. of 1,000 to 30,000 mPa·s.

[2] The lubricant base oil according to [1], in which the hydrocarbonoil satisfies the condition (i) and has an SBV viscosity at −30° C. of5,000 to 500,000 mPa·s.

[3] The lubricant base oil according to [1] or [2], in which thehydrocarbon oil satisfies the condition (i) and has a freezing point of−20 to −5° C.

[4] The lubricant base oil according to any one of [1] to [3], in whichthe hydrocarbon oil satisfies the condition (i) and has a ratio of CH₂carbons constituting a main chain to all carbons constituting thelubricant base oil of 15% or more in a ¹³C-NMR analysis.

[5] The lubricant base oil according to any one of [1] to [4], in whichthe hydrocarbon oil satisfies the condition (i) and has a cycloparaffincontent of 50% or less in an FD-MS analysis.

[6] The lubricant base oil according to [I], in which the hydrocarbonoil satisfies the condition (ii) and has an SBV viscosity at −25° C. of5,000 to 500,000 mPa·s.

[7] The lubricant base oil according to [1] or [6], in which thehydrocarbon oil satisfies the condition (ii) and has a freezing point of−15 to −5° C.

[8] The lubricant base oil according to any one of [1], [6] and [7], inwhich the hydrocarbon oil satisfies the condition (ii) and has a ratioof CH₂ carbons constituting a main chain to all carbons constituting thelubricant base oil of 20% or more in a ¹³C-NMR analysis.

[9] The lubricant base oil according to any one of [1], [6], [7] and[8], in which the hydrocarbon oil satisfies the condition (ii) and has acycloparaffin content of 60% or less in an FD-MS analysis.

[10] The lubricant base oil according to [1], in which the hydrocarbonoil satisfies the condition (iii) and has an SBV viscosity at −35° C. of3,000 to 500,000 mPa·s.

[11] The lubricant base oil according to [1] or [10], in which thehydrocarbon oil satisfies the condition (iii) and has a freezing pointof −30 to −10° C.

[12] The lubricant base oil according to any one of [1], [10] and [11],in which the hydrocarbon oil satisfies the condition (iii) and has aratio of CH₂ carbons constituting a main chain to all carbonsconstituting the lubricant base oil of 15% or more in a ¹³C-NMRanalysis.

[13] The lubricant base oil according to any one of [1], [10], [11] and[12], in which the hydrocarbon oil satisfies the condition (iii) and hasa cycloparaffin content of 30% or less in an FD-MS analysis.

[14] A method for producing a lubricant base oil, the method including

a first step of fractionating, from a hydrocarbon oil containing a baseoil fraction and a heavy fraction that is heavier than the base oilfraction, the base oil fraction and the heavy fraction,

a second step of returning a cracked oil obtained by hydrocracking theheavy fraction fractionated in the first step, to the first step,

a third step of obtaining a dewaxed oil by performing hydroisomerizationdewaxing of the base oil fraction,

a fourth step of obtaining a refined oil by refining the dewaxed oil,and

a fifth step of obtaining a lubricant base oil that is a hydrocarbon oilthat satisfies any of the following conditions (i), (ii) and (iii):

(i) a hydrocarbon oil having a kinematic viscosity at 100° C. of 3.0 to5.0 mm²/s, a viscosity index of 145 or more, and an SBV viscosity at−20° C. of 3,000 to 60,000 mPa·s,

(ii) a hydrocarbon oil having a kinematic viscosity at 100° C. of 5 to 9mm²/s, a viscosity index of 155 or more, and an SBV viscosity at −20° C.of 3,000 to 30,000 mPa·s, and

(iii) a hydrocarbon oil having a kinematic viscosity at 100° C. of 2.0to 3.0 mm²/s, a viscosity index of 130 or more, and an SBV viscosity at−30° C. of 1,000 to 30,000 mPa·s by fractionation of the refined oil.

[15] The method according to [14], in which the lubricant base oilobtained in the third step satisfies the condition (i) and has afreezing point of −20 to −5° C.

[16] The method according to [14], in which the lubricant base oilobtained in the third step satisfies the condition (ii) and has afreezing point of −15 to −5° C.

[17] The method according to [14], in which the lubricant base oilobtained in the third step satisfies the condition (iii) and has afreezing point of −30 to −10° C.

[18] The method according to any one of [14] to [17], in which the thirdstep is a step of performing hydroisomerization dewaxing of the base oilfraction in the presence of a hydroisomerization catalyst containing atleast one crystalline solid acidic substance selected from the groupconsisting of ZSM-22-type zeolite, ZSM-23-type zeolite, SSZ32, andZSM-48-type zeolite and platinum and/or palladium as an active metal.

[19] The method according to any one of [14] to [18], in which thehydrocarbon oil is obtained by using GTL wax obtained by aFischer-Tropsch synthesis or slack wax obtained by solvent dewaxing, asa raw material.

Here, the kinematic viscosity and the viscosity index in the presentinvention mean a kinematic viscosity and a viscosity index measured inconformity with JIS K 2283-1993, respectively.

Moreover, the SBV viscosity in the present invention means a valuemeasured by a method in which a viscosity is continuously measured byrotating a rotor at 0.3 rpm while cooling at a cooling rate of 1°C./hour, which is a test method defined in ASTM D5133.

Moreover, the freezing point in the present invention means a valuemeasured according to the following procedure.

More specifically, a sample charged in a test tube is preheated to 46°C., and then, is cooled at 2.5° C./min, and a cooling rate is changed to1° C./min at a temperature higher than an expected freezing point(measured once in advance) by 10° C. to start the measurement. Accordingto this method, a reproducible freezing point can be obtained comparedto JIS. This freezing point is distinguished from a pour point measuredby JIS K 2269-1987 (JIS method pour point). In addition, according tothe study of the present inventors, the pour point defined in JIS issuitable for measuring a liquid having widely differing crystallizationtemperatures, such as a petroleum lubricant base oil that is amulticomponent mixture. However, in the case of the present invention, asingle component of paraffin does not flow by the JIS measurement methodfor evaluating fluidity when being inclined, but is confirmed to flow bythe application of exogenous force and does not exhibit actual fluidity.The cause is due to the composition and is also affected by a rate oftemperature decrease of 2.5° C./min, and determination in a situationwhere crystallization does not proceed completely is considered to bethe cause. Therefore, it is necessary to accelerate fluidity of base oilmolecules and to obtain a freezing point close to a true value byslowing a descending rate of temperature.

Moreover, the ratio of CH₂ carbons constituting the main chain to allcarbons constituting the lubricant base oil can be determined, forexample, by performing a ¹³C-NMR analysis under the following analysisconditions.

More specifically, in the present invention, in the ¹³C-NMR measurement,a diluted sample obtained by adding 3 g of deuterated chloroform to 0.5g of a sample was used, the measurement temperature was roomtemperature, and the resonant frequency was 100 MHz. In addition, agated decoupling method was used as the measurement method.

The ratio of CH₂ to the total of the constituent carbons of thelubricant base oil of the present invention means a ratio of the totalof integral intensity attributed to the CH₂ main chain with respect tothe total of integral intensity of all carbons, which are measured by¹³C-NMR, and other methods may be used as long as the equivalent resultis obtained.

Furthermore, the ratio of the cycloparaffin content can be determined,for example, by performing an FD-MS analysis under the followinganalysis conditions.

The FD method is an ionization method in which a sample is coated on anemitter, a current is applied to the emitter to heat the coated sample,and a tunneling effect is used in a high electrical field on the emittersurface and in the vicinity of the whisker tip. In the presentinvention, the measurement was performed using JMS-AX505H by JEOL Ltd.under conditions of an accelerating voltage (cathode voltage) of 3.0 kVand an emitter current of 2 mA/min. Compound types in mass spectrometryare determined by specific ions to be formed, and they are generallyclassified by a z value. The z value is represented by a general formulaC_(n)H_(2n+z) for all hydrocarbon species. Since the saturated phase isanalyzed separately from the aromatic phase, contents of differentcycloparaffins having the same stoichiometry can be measured. Inaddition, cycloparaffins include both of monocyclic cycloparaffins andbicyclic or more cycloparaffins.

Advantageous Effects of Invention

According to the present invention, a lubricant base oil capable ofsatisfying both a low-temperature viscosity characteristic and a sealingproperty at a high level, and a method for producing same are provided.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention will now be described inmore detail.

First Embodiment Lubricant Base Oil that is Hydrocarbon Oil thatSatisfies Condition (i)

The lubricant base oil according to the first embodiment of the presentinvention is a lubricant base oil that is a hydrocarbon oil having akinematic viscosity at 100° C. of 3.0 to 5.0 mm²/s and an SBV viscosityat −20° C. of 3,000 to 60,000 mPa·s.

In addition, conventionally, a pour point used as an index of alow-temperature viscosity characteristic of a lubricant base oilevaluates ease of flow, that is to say, a bulk viscosity. In contrast,the SBV viscosity in the present invention can evaluate not a bulkviscosity but mobility of a base oil at the molecular level. Forexample, a lubricant base oil does not flow at a temperature lower thana pour point, but can move at the molecular level due to distortionbetween molecules constituting the base oil to impart the SBV viscosity.The lubricant base oil according to the present embodiment is made basedon the above-described present inventors' knowledge, and has anunexpected significant effect that, in a lubricant base oil having akinematic viscosity at 100° C. of 3.0 to 5.0 mm²/s and a viscosity indexof 145 or more, by making the SBV viscosity at −20° C. of the lubricantbase oil be 3,000 to 60,000 mPa·s, a sealing property can be improvedwhile sufficiently maintaining a low-temperature viscositycharacteristic.

The kinematic viscosity of the lubricant base oil according to thepresent embodiment at 100° C. is 3.0 to 5.0 mm²/s, preferably 3.0 to 4.5mm²/s, more preferably 3.2 to 4.3 mm²/s, and more preferably 3.4 to 4.1mm²/s.

Moreover, the viscosity index of the lubricant base oil according to thepresent embodiment is 145 or more, preferably 147 or more, and morepreferably 148 to 160. In addition, if the viscosity index is less thanthe above-described lower limit, an energy saving property is decreased,and if it exceeds the above-described upper limit, fluidity at ordinarytemperature is decreased and the lubricant base oil according to thepresent embodiment tends to be not able to be used as a lubricant baseoil.

Moreover, the SBV viscosity of the lubricant base oil according to thepresent embodiment at −20° C. is 3,000 to 60,000 mPa·s, preferably 3,000to 30,000 mPa·s, and more preferably 3,000 to 15,000 mPa·s. If the SBVviscosity at −20° C. is less than the above-described lower limit, asealing property is insufficient, and if it exceeds the above-describedupper limit, a low temperature viscosity characteristic is insufficient.

Moreover, the SBV viscosity of the lubricant base oil according to thepresent embodiment at −30° C. is preferably 50,000 to 500,000 mPa·s,more preferably 50,000 to 400,000 in mPa·s, and further preferably50,000 to 300,000 mPa·s. If the SBV viscosity at −25° C. is less thanthe above-described lower limit, a sealing property becomesinsufficient, and if it exceeds the above-described upper limit, a lowtemperature viscosity characteristic becomes insufficient.

Moreover, the kinematic viscosity of the lubricant base oil according tothe present embodiment at 40° C. is preferably 10 to 20 mm²/s, and morepreferably 12 to 16 mm²/s.

Moreover, the freezing point of the lubricant base oil according to thepresent embodiment is preferably −20 to −5° C., more preferably −18 to−8° C., and further preferably −15 to −10° C. In addition, if thefreezing point is less than the above-described lower limit, an energysaving property tends to be decreased, and if it exceeds theabove-described upper limit, fluidity at ordinary temperature tends tobe decreased and the lubricant base oil according to the presentembodiment cannot be used as a lubricant base oil.

Furthermore, in the case of performing a ¹³C-NMR analysis of thelubricant base oil according to the present embodiment, a ratio of CH₂carbons constituting the main chain to all carbons constituting thelubricant base oil is preferably 15% or more, and more preferably 16% ormore. If the ratio is the above-described lower limit or more, atraction coefficient of the lubricant base oil can be decreased (thatis, low friction), and it is preferable in terms of an energy savingproperty.

Furthermore, in the case of performing an FD-MS analysis of thelubricant base oil according to the present embodiment, a cycloparaffincontent is preferably 50% or less, and more preferably 40% or less. Ifthe cycloparaffin content is the above-described upper limit or less,abrasion resistance of the lubricant base oil can be further improved.

Moreover, from the viewpoint of improving a low-temperature viscositycharacteristic without impairing a viscosity-temperature characteristicat high temperature, the urea adduct value of the lubricant base oilaccording to the present embodiment is preferably 4% by mass or less,more preferably 3.5% by mass or less, further preferably 3% by mass orless, and particularly preferably 2.5% by mass or less. Furthermore, theurea adduct value of the lubricant base oil may be 0% by mass. However,since a sufficient low-temperature viscosity characteristic and alubricant base oil having a higher viscosity index can be obtained, andfurthermore, dewaxing conditions are loosened to result in excellenteconomic efficiency, it is preferably 0.1% by mass or more, morepreferably 0.5% by mass or more, and particularly preferably 0.8% bymass or more.

Moreover, the content of the saturated content in the lubricant base oilaccording to the present embodiment is, on the basis of the total amountof the lubricant base oil, preferably 90% by mass or more, morepreferably 93% by mass or more, further preferably 95% by mass or more,and particularly preferably 99% by mass or more. The content of thesaturated content satisfies the above-described condition so that aviscosity-temperature characteristic and thermal-oxidation stability canbe achieved, and furthermore, in the case where an additive agent isblended into the lubricant base oil, the additive agent is sufficientlystably dissolved and maintained in the lubricant base oil and functionsof the additive agent can be expressed at a high level. Furthermore, afriction characteristic of the lubricant base oil itself can beimproved, and as a result, improvement in a friction-reducing effect andtherefore improvement in an energy saving property can be achieved. Inaddition, the content of the saturated content in the present inventionmeans a value (unit: % by mass) measured in conformity with ASTM D2007-93.

Moreover, the aromatic content in the lubricant base oil according tothe present embodiment is, on the basis of the total amount of thelubricant base oil, preferably 5% by mass or less, more preferably 0.05to 3% by mass, further preferably 0.1 to 1% by mass, and particularlypreferably 0.1 to 0.5% by mass. If the content of the aromatic contentexceeds the above-described upper limit, a viscosity-temperaturecharacteristic, thermal-oxidation stability, a friction characteristic,and furthermore, a volatilization-preventing property, and alow-temperature viscosity characteristic tend to be decreased, andmoreover, in the case where an additive agent is blended into thelubricant base oil, an effect of the additive agent tends to bedecreased. Furthermore, although the lubricant base oil according to thepresent embodiment may not contain the aromatic content, solubility ofthe additive agent can be further increased by making the content of thearomatic content be 0.05% by mass or more.

In addition, the content of the aromatic content in the presentinvention means a value measured in conformity with ASTM D 2007-93.Generally, the aromatic content includes, in addition to alkylbenzenesand alkylnaphthalenes, anthracene, phenanthrene, alkylated productsthereof, and moreover, compounds in which four benzene rings or more arecondensed, and aromatic compounds having a hetero atom, such aspyridines, quinolines, phenols, and naphthols.

Furthermore, the content of the sulfur content in the lubricant base oilaccording to the present embodiment depends on the content of the sulfurcontent in the raw material. For example, in the case of using a rawmaterial substantially not containing sulfur, such as a synthetic waxconstituent obtained by a Fischer-Tropsch reaction or the like, alubricant base oil substantially not containing sulfur can be obtained.Moreover, in the case of using a raw material containing sulfur, such asslack wax obtained in the refining process of the lubricant base oil andmicro wax obtained in the wax refining process, the sulfur content inthe obtained lubricant base oil is generally 100 mass ppm or more. Inthe lubricant base oil of the present invention, in terms of furtherimprovement in thermal-oxidation stability and reduction in the sulfurcontent, the content of the sulfur content is preferably 10 mass ppm orless, more preferably 5 mass ppm or less, further preferably 3 mass ppmor less, and particularly preferably 1 mass ppm or less.

Furthermore, in terms of cost reduction, slack wax or the like ispreferably used as a raw material, and in this case, the sulfur contentin the obtained lubricant base oil is preferably 50 mass ppm or less,and more preferably 10 mass ppm or less. In addition, the sulfur contentin the present invention means a sulfur content measured in conformitywith HS K 2541-1996.

Moreover, the pour point of the lubricant base oil according to thepresent embodiment is preferably −5° C. or less, more preferably −10° C.or less, and further preferably −12.5° C. or less. If the pour pointexceeds the above-described upper limit, low temperature fluidity of theentire lubricant oil using the lubricant base oil tends to be decreased.Furthermore, the pour point of the lubricant base oil according to thepresent embodiment is preferably −20° C. or more, more preferably −17.5°C. or more, and further preferably −15° C. or more. If the pour point isless than −20° C., it becomes difficult for the SBV viscosity at −20° C.to be within a range of 3,000 to 60,000 in mPa·s, and a sealing propertytends to be insufficient. In addition, the pour point in the presentinvention means a pour point measured in conformity with HS K 2269-1987.

Moreover, the CCS viscosity of the lubricant base oil according to thepresent embodiment at −30° C. is preferably 1,500 in mPa·s or less, andmore preferably 1,200 mPa·s or less. Furthermore, the CCS viscosity ofthe lubricant base oil at −35° C. is preferably 2,500 mPa·s or less, andmore preferably 2,000 mPa·s or less. If the CCS viscosity at −30° C. orat −35° C. exceeds the above-described upper limit, low temperaturefluidity of the entire lubricant oil using the lubricant base oil tendsto be decreased. In addition, the CCS viscosity at −30° C. or at −35° C.means a viscosity measured in conformity with JIS K 2010-1993.

Moreover, the density of the lubricant base oil according to the presentembodiment at 15° C. (ρ₁₅) is preferably a ρ value represented by thefollowing formula (I) or less, that is ρ₁₅≦ρ.

ρ=0.0025×kv100+0.816  (1)

[In the formula, kv100 represents kinematic viscosity of lubricant baseoil at 100° C. (min²/s).]

In addition, in the case of ρ₁₅>ρ, a viscosity-temperaturecharacteristic, thermal-oxidation stability, and furthermore, avolatilization-preventing property, and a low-temperature viscositycharacteristic tend to be decreased, and moreover, in the case where anadditive agent is blended into the lubricant base oil, an effect of theadditive agent tends to be decreased.

More specifically, ρ₁₅ of the lubricant base oil is preferably 0.815 orless, and more preferably 0.810 or less.

In addition, the density at 15° C. in the present invention means adensity measured at 15° C. in conformity with JIS K 2249-1995.

Moreover, the NOACK evaporation of the lubricant base oil according tothe present embodiment is preferably 8% by mass or more, more preferably9% by mass or more, further preferably 10 or more, and moreover,preferably 15% by mass or less, more preferably 14% by mass or less, andfurther preferably 13% by mass or less. When the NOACK evaporation isthe above-described lower limit, improvement in a low-temperatureviscosity characteristic tends to become difficult. Furthermore, theNOACK evaporation exceeding the above-described upper limit is notpreferable because, in the case where the lubricant base oil is used foran internal combustion engine lubricant oil or the like, evaporationloss of the lubricant oil is increased, and therefore, catalystpoisoning is accelerated. In addition, the NOACK evaporation in thepresent invention means evaporation loss measured in conformity withASTM D 5800-95.

Second Embodiment Lubricant Base Oil that is Hydrocarbon Oil thatSatisfies Condition (ii)

The lubricant base oil according to the second embodiment of the presentinvention is a hydrocarbon oil having a kinematic viscosity at 100° C.of 5 to 9 mm²/s and an SBV viscosity at −20° C. of 3,000 to 30,000mPa·s.

In addition, conventionally, a pour point used as an index of alow-temperature viscosity characteristic of a lubricant base oilevaluates ease of flow, that is to say, a bulk viscosity. In contrast,the SBV viscosity in the present invention can evaluate not a bulkviscosity but mobility of a base oil at the molecular level. Forexample, a lubricant base oil does not flow at a temperature lower thana pour point, but can move at the molecular level due to distortionbetween molecules constituting the base oil to impart the SBV viscosity.The lubricant base oil according to the present embodiment is made basedon the above-described present inventors' knowledge, and has anunexpected significant effect that, in a lubricant base oil having akinematic viscosity at 100° C. of 5 to 9 mm²/s, by making the SBVviscosity at −20° C. of the lubricant base oil be 3,000 to 30,000 mPa·s,a sealing property can be improved while sufficiently maintaining alow-temperature viscosity characteristic.

The kinematic viscosity of the lubricant base oil according to thepresent embodiment at 100° C. is 5 to 9 mm²/s, preferably 5.5 to 8.5mm²/s, and more preferably 6 to 8 mm²/s.

Moreover, the SBV viscosity of the lubricant base oil according to thepresent embodiment at −20° C. is 3,000 to 30,000 in mPa·s, preferably3,000 to 25,000 mPa·s, and more preferably 3,000 to 20,000 in mPa·s. Ifthe SBV viscosity at −20° C. is less than the above-described lowerlimit, a sealing property is insufficient, and if it exceeds theabove-described upper limit, a low temperature viscosity characteristicis insufficient.

Moreover, the SBV viscosity of the lubricant base oil according to thepresent embodiment at −25° C. is preferably 5,000 to 500,000 mPa·s, morepreferably 5,000 to 400,000 mPa·s, and further preferably 5,000 to300,000 mPa·s. If the SBV viscosity at −25° C. is less than theabove-described lower limit, a sealing property becomes insufficient,and if it exceeds the above-described upper limit, a low temperatureviscosity characteristic becomes insufficient.

Moreover, the kinematic viscosity of the lubricant base oil according tothe present embodiment at 40° C. is preferably 25 to 40 mm²/s, and morepreferably 28 to 35 mm²/s.

Moreover, the viscosity index of the lubricant base oil according to thepresent embodiment is 155 or more, preferably 157 or more, and morepreferably 158 to 165. In addition, if the viscosity index is less thanthe above-described lower limit, an energy saving property is decreased,and if it exceeds the above-described upper limit, fluidity at ordinarytemperature tends to be decreased and the lubricant base oil accordingto the present embodiment cannot be used as a lubricant base oil.

Moreover, the freezing point of the lubricant base oil according to thepresent embodiment is preferably −15 to −5° C., more preferably −14 to−7° C., and further preferably −13 to −8° C. In addition, if thefreezing point is less than the above-described lower limit, an energysaving property tends to be decreased, and if it exceeds theabove-described upper limit, fluidity at ordinary temperature tends tobe decreased and the lubricant base oil according to the presentembodiment cannot be used as a lubricant base oil.

Furthermore, in the case of performing a ¹³C-NMR analysis of thelubricant base oil according to the present embodiment, a ratio of CH₂carbons constituting the main chain to all carbons constituting thelubricant base oil is preferably 20% or more, and more preferably 18% ormore. If the ratio is the above-described lower limit or more, atraction coefficient of the lubricant base oil can be decreased (thatis, low friction), and it is preferable in terms of an energy savingproperty.

Furthermore, in the case of performing an FD-MS analysis of thelubricant base oil according to the present embodiment, a cycloparaffincontent is preferably 60% or less, and more preferably 65% or less. Ifthe cycloparaffin content is the above-described upper limit or less,abrasion resistance of the lubricant base oil can be further improved.

Moreover, from the viewpoint of improving a low-temperature viscositycharacteristic without impairing a viscosity-temperature characteristicat high temperature, the urea adduct value of the lubricant base oilaccording to the present embodiment is preferably 4% by mass or less,more preferably 3.5% by mass or less, further preferably 3% by mass orless, and particularly preferably 2.5% by mass or less. Furthermore, theurea adduct value of the lubricant base oil may be 0% by mass. However,since a sufficient low-temperature viscosity characteristic and alubricant base oil having a higher viscosity index can be obtained, andfurthermore, dewaxing conditions are loosened to result in excellenteconomic efficiency, it is preferably 0.1% by mass or more, morepreferably 0.5% by mass or more, and particularly preferably 0.8% bymass or more.

Moreover, the content of the saturated content in the lubricant base oilaccording to the present embodiment is, on the basis of the total amountof the lubricant base oil, preferably 90% by mass or more, morepreferably 93% by mass or more, further preferably 95% by mass or more,and particularly preferably 99% by mass or more. The content of thesaturated content satisfies the above-described condition so that aviscosity-temperature characteristic and thermal-oxidation stability canbe achieved, and furthermore, in the case where an additive agent isblended into the lubricant base oil, the additive agent is sufficientlystably dissolved and maintained in the lubricant base oil and functionsof the additive agent can be expressed at a high level. Furthermore, afriction characteristic of the lubricant base oil itself can beimproved, and as a result, improvement in a friction-reducing effect andtherefore improvement in an energy saving property can be achieved.

Moreover, the aromatic content in the lubricant base oil according tothe present embodiment is, on the basis of the total amount of thelubricant base oil, preferably 5% by mass or less, more preferably 0.05to 3% by mass, further preferably 0.1 to 1% by mass, and particularlypreferably 0.1 to 0.5% by mass. If the content of the aromatic contentexceeds the above-described upper limit, a viscosity-temperaturecharacteristic, thermal-oxidation stability, a friction characteristic,and furthermore, a volatilization-preventing property, and alow-temperature viscosity characteristic tend to be decreased, andmoreover, in the case where an additive agent is blended into thelubricant base oil, an effect of the additive agent tends to bedecreased. Furthermore, although the lubricant base oil according to thepresent embodiment may not contain the aromatic content, solubility ofthe additive agent can be further increased by making the content of thearomatic content be 0.05% by mass or more.

Furthermore, the content of the sulfur content in the lubricant base oilaccording to the present embodiment depends on the content of the sulfurcontent in the raw material. For example, in the case of using a rawmaterial substantially not containing sulfur, such as a synthetic waxconstituent obtained by a Fischer-Tropsch reaction or the like, alubricant base oil substantially not containing sulfur can be obtained.Moreover, in the case of using a raw material containing sulfur, such asslack wax obtained in the refining process of the lubricant base oil andmicro wax obtained in the wax refining process, the sulfur content inthe obtained lubricant base oil is generally 100 mass ppm or more. Inthe lubricant base oil of the present invention, in terms of furtherimprovement in thermal-oxidation stability and reduction in the sulfurcontent, the content of the sulfur content is preferably 10 mass ppm orless, more preferably 5 mass ppm or less, further preferably 3 mass ppmor less, and particularly preferably 1 mass ppm or less.

Furthermore, in terms of cost reduction, slack wax or the like ispreferably used as a raw material, and in this case, the sulfur contentin the obtained lubricant base oil is preferably 50 mass ppm or less,and more preferably 10 mass ppm or less.

Moreover, the pour point of the lubricant base oil according to thepresent embodiment is preferably −5° C. or less, more preferably −10° C.or less, and further preferably −12.5° C. or less. If the pour pointexceeds the above-described upper limit, low temperature fluidity of theentire lubricant oil using the lubricant base oil tends to be decreased.Furthermore, the pour point of the lubricant base oil according to thepresent embodiment is preferably −20° C. or more, more preferably −17.5°C. or more, and further preferably −15° C. or more. If the pour point isless than −20° C., it becomes difficult for the SBV viscosity at −20° C.to be within a range of 3,000 to 30,000 mPa·s, and a sealing propertytends to be insufficient.

Moreover, the CCS viscosity of the lubricant base oil according to thepresent embodiment at −30° C. is preferably 950 mPa·s or less, and morepreferably 900 mPa·s or less. Furthermore, the CCS viscosity of thelubricant base oil at −35° C. is preferably 1,600 mPa·s or less, andmore preferably 1,500 mPa·s or less. If the CCS viscosity at −30° C. orat −35° C. exceeds the above-described upper limit, low temperaturefluidity of the entire lubricant oil using the lubricant base oil tendsto be decreased.

Moreover, the density of the lubricant base oil according to the presentembodiment at 15° C. (ρ₁₅) is preferably a ρ value represented by thefollowing formula (1) or less, that is ρ₁₅≦ρ.

ρ=0.0025×kv100+0.816  (1)

[In the formula, kv100 represents kinematic viscosity of lubricant baseoil at 100° C. (mm²/s).]

In addition, in the case of ρ₁₅>ρ, a viscosity-temperaturecharacteristic, thermal-oxidation stability, and furthermore, avolatilization-preventing property, and a low-temperature viscositycharacteristic tend to be decreased, and moreover, in the case where anadditive agent is blended into the lubricant base oil, an effect of theadditive agent tends to be decreased.

More specifically, ρ₁₅ of the lubricant base oil is preferably 0.830 orless, and more preferably 0.825 or less.

Third Embodiment Lubricant Base Oil that is Hydrocarbon Oil thatSatisfies Condition (iii)

The lubricant base oil according to the third embodiment of the presentinvention is a lubricant base oil that is a hydrocarbon oil having akinematic viscosity at 100° C. of 2.0 to 3.0 mm²/s, a viscosity index of130 or more, and an SBV viscosity at −30° C. of 1,000 to 30,000 mPa·s.

In addition, conventionally, a pour point used as an index of alow-temperature viscosity characteristic of a lubricant base oilevaluates ease of flow, that is to say, a bulk viscosity. In contrast,the SBV viscosity in the present invention can evaluate not a bulkviscosity but mobility of a base oil at the molecular level. Forexample, a lubricant base oil does not flow at a temperature lower thana pour point, but can move at the molecular level due to distortionbetween molecules constituting the base oil to impart the SBV viscosity.The lubricant base oil according to the present embodiment is made basedon the above-described present inventors' knowledge, and has anunexpected significant effect that, in a lubricant base oil having akinematic viscosity at 100° C. of 2.0 to 3.0 mm²/s and a viscosity indexof 130 or more, by making the SBV viscosity at −30° C. of the lubricantbase oil be 1,000 to 30,000 in mPa·s, a sealing property can be improvedwhile sufficiently maintaining a low-temperature viscositycharacteristic.

The kinematic viscosity of the lubricant base oil according to thepresent embodiment at 100° C. is 2.0 to 3.0 mm²/s, preferably 2.1 to 2.9mm²/s, and more preferably 2.2 to 2.8 mm²/s.

Moreover, the viscosity index of the lubricant base oil according to thepresent embodiment is 130 or more, preferably 131 or more, and morepreferably 132 to 140. If the viscosity index is less than theabove-described lower limit, an energy saving property is decreased, andif it exceeds the above-described upper limit, fluidity at ordinarytemperature is decreased and the lubricant base oil according to thepresent embodiment cannot be used as a lubricant base oil.

Moreover, the SBV viscosity of the lubricant base oil according to thepresent embodiment at −30° C. is 1,000 to 30,000 mPa·s, preferably 1,000to 20,000 mPa·s, and more preferably 1,000 to 15,000 mPa·s. If the SBVviscosity at −30° C. is less than the above-described lower limit, asealing property is insufficient, and if it exceeds the above-describedupper limit, a low temperature characteristic is insufficient.

Moreover, the SBV viscosity of the lubricant base oil according to thepresent embodiment at −35° C. is preferably 3,000 to 500,000 in mPa·s,more preferably 3,000 to 400,000 in mPa·s, and further preferably 3,000to 300,000 mPa·s. If the SBV viscosity at −35° C. is less than theabove-described lower limit, a sealing property is insufficient, and ifit exceeds the above-described upper limit, a low-temperature viscositycharacteristic is insufficient.

Moreover, the SBV viscosity of the lubricant base oil according to thepresent embodiment at −40° C. is preferably 5,000 to 750,000 in mPa·s,more preferably 5,000 to 500,000 mPa·s, and further preferably 5,000 to400,000 mPa·s. If the SBV viscosity at −40° C. is less than theabove-described lower limit, a sealing property is insufficient, and ifit exceeds the above-described upper limit, a low-temperature viscositycharacteristic is insufficient.

Moreover, the kinematic viscosity of the lubricant base oil according tothe present embodiment at 40° C. is preferably 7 to 12 mm²/s, and morepreferably 8 to 10 mm²/s.

Moreover, the freezing point of the lubricant base oil according to thepresent embodiment is preferably −30 to −10° C., more preferably −29 to−15° C., and further preferably −28 to −20° C. In addition, if thefreezing point is less than the above-described lower limit, an energysaving property tends to be decreased, and if it exceeds theabove-described upper limit, fluidity at ordinary temperature tends tobe decreased and the lubricant base oil according to the presentembodiment cannot be used as a lubricant base oil.

Furthermore, in the case of performing a ¹³C-NMR analysis of thelubricant base oil according to the present embodiment, a ratio of CH₂carbons constituting the main chain to all carbons constituting thelubricant base oil is preferably 15% or more, and more preferably 15% ormore. If the ratio is the above-described lower limit or more, atraction coefficient of the lubricant base oil can be decreased (thatis, low friction), and it is preferable in terms of an energy savingproperty.

Furthermore, in the case of performing an FD-MS analysis of thelubricant base oil according to the present embodiment, a cycloparaffincontent is preferably 30% or less, and more preferably 25% or less. Ifthe cycloparaffin content is the above-described upper limit or less,abrasion resistance of the lubricant base oil can be further improved.

Moreover, from the viewpoint of improving a low-temperature viscositycharacteristic without impairing a viscosity-temperature characteristicat high temperature, the urea adduct value of the lubricant base oilaccording to the present embodiment is preferably 4% by mass or less,more preferably 3.5% by mass or less, further preferably 3% by mass orless, and particularly preferably 2.5% by mass or less. Furthermore, theurea adduct value of the lubricant base oil may be 0% by mass. However,since a sufficient low-temperature viscosity characteristic and alubricant base oil having a higher viscosity index can be obtained, andfurthermore, dewaxing conditions are loosened to result in excellenteconomic efficiency, it is preferably 0.1% by mass or more, morepreferably 0.5% by mass or more, and particularly preferably 0.8% bymass or more.

Moreover, the content of the saturated content in the lubricant base oilaccording to the present embodiment is, on the basis of the total amountof the lubricant base oil, preferably 90% by mass or more, morepreferably 93% by mass or more, further preferably 95% by mass or more,and particularly preferably 99% by mass or more. The content of thesaturated content satisfies the above-described condition so that aviscosity-temperature characteristic and thermal-oxidation stability canbe achieved, and furthermore, in the case where an additive agent isblended into the lubricant base oil, the additive agent is sufficientlystably dissolved and maintained in the lubricant base oil and functionsof the additive agent can be expressed at a high level. Furthermore, afriction characteristic of the lubricant base oil itself can beimproved, and as a result, improvement in a friction-reducing effect andtherefore improvement in an energy saving property can be achieved.

Moreover, the aromatic content in the lubricant base oil according tothe present embodiment is, on the basis of the total amount of thelubricant base oil, preferably 5% by mass or less, more preferably 0.05to 3% by mass, further preferably 0.1 to 1% by mass, and particularlypreferably 0.1 to 0.5% by mass. If the content of the aromatic contentexceeds the above-described upper limit, a viscosity-temperaturecharacteristic, thermal-oxidation stability, a friction characteristic,and furthermore, a volatilization-preventing property, and alow-temperature viscosity characteristic tend to be decreased, andmoreover, in the case where an additive agent is blended into thelubricant base oil, an effect of the additive agent tends to bedecreased. Furthermore, although the lubricant base oil according to thepresent embodiment may not contain the aromatic content, solubility ofthe additive agent can be further increased by making the content of thearomatic content be 0.05% by mass or more.

Furthermore, the content of the sulfur content in the lubricant base oilaccording to the present embodiment depends on the content of the sulfurcontent in the raw material. For example, in the case of using a rawmaterial substantially not containing sulfur, such as a synthetic waxconstituent obtained by a Fischer-Tropsch reaction or the like, alubricant base oil substantially not containing sulfur can be obtained.Moreover, in the case of using a raw material containing sulfur, such asslack wax obtained in the refining process of the lubricant base oil andmicro wax obtained in the wax refining process, the sulfur content inthe obtained lubricant base oil is generally 100 mass ppm or more. Inthe lubricant base oil of the present invention, in terms of furtherimprovement in thermal-oxidation stability and reduction in the sulfurcontent, the content of the sulfur content is preferably 10 mass ppm orless, more preferably 5 mass ppm or less, further preferably 3 mass ppmor less, and particularly preferably 1 mass ppm or less.

Furthermore, in terms of cost reduction, slack wax or the like ispreferably used as a raw material, and in this case, the sulfur contentin the obtained lubricant base oil is preferably 50 mass ppm or less,and more preferably 10 mass ppm or less.

Moreover, the pour point of the lubricant base oil according to thepresent embodiment is preferably −5° C. or less, more preferably −12.5°C. or less, and further preferably −15° C. or less. If the pour pointexceeds the above-described upper limit, low temperature fluidity of theentire lubricant oil using the lubricant base oil tends to be decreased.Furthermore, the pour point of the lubricant base oil according to thepresent embodiment is preferably −27.5° C. or more, and more preferably−25° C. or more. If the pour point is less than −27.5° C., it becomesdifficult for the SBV viscosity at −20° C. to be within a range of 3,000to 60,000 mPa·s, and a sealing property tends to be insufficient.

Moreover, the CCS viscosity of the lubricant base oil according to thepresent embodiment at −30° C. is preferably 1,000 mPa·s or less, andmore preferably 750 mPa·s or less. Furthermore, the CCS viscosity of thelubricant base oil at −35° C. is preferably 1,300 mPa·s or less, andmore preferably 1,000 mPa·s or less. If the CCS viscosity at −30° C. orat −35° C. exceeds the above-described upper limit, low temperaturefluidity of the entire lubricant oil using the lubricant base oil tendsto be decreased.

Moreover, the density of the lubricant base oil according to the presentembodiment at 15° C. (ρ₁₅) is preferably a ρ value represented by thefollowing formula (1) or less, that is ρ₁₅≦ρ.

ρ=0.0025×kv100+0.816  (1)

[In the formula, kv100 represents kinematic viscosity of lubricant baseoil at 100° C. (mm²/s).]

In addition, in the case of ρ₁₅>ρ, a viscosity-temperaturecharacteristic, thermal-oxidation stability, and furthermore, avolatilization-preventing property, and a low-temperature viscositycharacteristic tend to be decreased, and moreover, in the case where anadditive agent is blended into the lubricant base oil, an effect of theadditive agent tends to be decreased.

More specifically, ρ₁₅ of the lubricant base oil is preferably 0.806 orless, and more preferably 0.8058 or less.

Moreover, the NOACK evaporation of the lubricant base oil according tothe present embodiment is preferably 20% by mass or more, morepreferably 25% by mass or more, further preferably 30 or more, andmoreover, preferably 50% by mass or less, more preferably 48% by mass orless, and further preferably 46% by mass or less. When the NOACKevaporation is the above-described lower limit, improvement in alow-temperature viscosity characteristic tends to become difficult.Furthermore, the NOACK evaporation exceeding the above-described upperlimit is not preferable because, in the case where the lubricant baseoil is used for an internal combustion engine lubricant oil or the like,evaporation loss of the lubricant oil is increased, and therefore,catalyst poisoning is accelerated.

Fourth Embodiment Method for Producing Lubricant Base Oil

The method for producing a lubricant base oil according to the fourthembodiment of the present invention includes

a first step of fractionating, from a hydrocarbon oil containing a baseoil fraction and a heavy fraction that is heavier than the base oilfraction, the base oil fraction and the heavy fraction,

a second step of returning a cracked oil obtained by hydrocracking theheavy fraction fractionated in the first step, to the first step,

a third step of obtaining a dewaxed oil by performing hydroisomerizationdewaxing of the base oil fraction,

a fourth step of obtaining a refined oil by refining the dewaxed oil,and

a fifth step of obtaining a lubricant base oil that is a hydrocarbon oilthat satisfies any of the following conditions (i), (ii) and (iii):

(i) a hydrocarbon oil having a kinematic viscosity at 100° C. of 3.0 to5.0 mm²/s, a viscosity index of 145 or more, and an SBV viscosity at−20° C. of 3,000 to 60,000 mPa·s,

(ii) a hydrocarbon oil having a kinematic viscosity at 100° C. of 5 to 9mm²/s, a viscosity index of 155 or more, and an SBV viscosity at −20° C.of 3,000 to 30,000 mPa·s, and

(iii) a hydrocarbon oil having a kinematic viscosity at 100° C. of 2.0to 3.0 mm²/s, a viscosity index of 130 or more, and an SBV viscosity at−30° C. of 1,000 to 30,000 mPa·s, by fractionation of the refined oil.

In the method for producing a lubricant base oil according to thepresent embodiment, the base oil fraction and the heavy fraction arefractionated from the hydrocarbon oil as a raw material (first step),and the cracked oil obtained by hydrocracking the heavy fraction isreturned to the first step (second step). That is, since only the heavyfraction is offered to the subsequent hydroisomerization dewaxing (thirdstep) after passing through the hydrocracking and the base oil fractionis offered to hydroisomerization dewaxing without passing through thehydrocracking, isomerization of the entire treated oil to be offered tohydroisomerization dewaxing becomes difficult to proceed compared to theconventional method for producing a highly-refined mineral oil. Then,with respect to such a treated oil, hydroisomerization dewaxing isperformed, the obtained dewaxed oil is refined to obtain the refined oil(fourth step), and furthermore, the refined oil is fractionated (fifthstep) so that the intended lubricant base oil can be effectivelyobtained.

In addition, as the conventional method for producing a highly-refinedmineral oil, hydrocracking and hydroisomerization dewaxing are generallyperformed for entire feedstock, but in this case, it becomes difficultto obtain a lubricant base oil in which both of a kinematic viscosity at100° C. and an SBV viscosity at −20° C. satisfy the above-describedconditions. In particular, in the case of a conventional highly-refinedmineral oil, if the kinematic viscosity at 100° C. is within the rangeshown in any of the above-described (i), (ii) and (iii), the SBVviscosity at −30° C. is less than the lower limit shown in therespective conditions, and a sealing property becomes insufficient.

The base oil fraction is a fraction for obtaining a lubricant base oilafter a dewaxing step, a hydrofinishing step, and a second distillationstep, and the boiling point range thereof can be appropriately changedbased on the intended product. Examples of the preferred boiling pointrange of the base oil fraction in the present embodiment include 340 to520° C.

The heavy fraction is a fraction that has a higher boiling point thanthe base oil fraction. It is preferred that a boiling point of the heavyfraction is higher than 520° C.

The hydrocarbon oil may also contain, other than the base oil fractionand the heavy fraction, a fraction (light fraction) that has a lowerboiling point than the base oil fraction. It is preferred that a boilingpoint of the light fraction is lower than 340° C.

Examples of the hydrocarbon oil include hydrotreated or hydrocracked gasoil, heavy gas oil, vacuum gas oil, lubricant oil raffinate, lubricantoil raw material, bright stock, slack wax (crude wax), foot's oil,deoiled wax, paraffinic wax, microcrystalline wax, petrolatum, syntheticoils, Fischer-Tropsch synthesis reaction oil (hereinafter referred to asan “FT synthetic oil”), high-pour-point polyolefins, and straight-chainα-olefin waxes. These hydrocarbon oils can be used singly or incombinations of two or more. In particular, the hydrocarbon oil ispreferably at least one selected from the group consisting of a vacuumgas oil, a hydrocracked vacuum gas oil, an atmospheric residue, ahydrocracked atmospheric residue, a vacuum residue, a hydrocrackedvacuum residue, slack wax, a dewaxed oil, paraffin wax, microcrystallinewax, petrolatum, and Fischer-Tropsch synthetic wax, and furtherpreferably at least one selected from the group consisting of anatmospheric residue, a vacuum residue, a vacuum gas oil, slack wax, andFischer-Tropsch synthetic wax.

In one aspect of the present invention, FT (Fischer-Tropsch) syntheticoil is preferred as the hydrocarbon oil. The FT synthetic oil is ahydrocarbon oil synthesized from carbon monoxide and hydrogen by a FTsynthesis reaction, and does not contain a nitrogen content. Therefore,when the hydrocarbon oil is the FT synthetic oil, there is nopossibility of sulfur poisoning in hydrocracking and isomerizationdewaxing described below, and a wide variety of catalysts can be used.

Further, in another aspect of the present invention, it is preferred touse as the hydrocarbon oil a petroleum-based hydrocarbon oil containingpetroleum feedstock-derived hydrocarbons. Examples of thepetroleum-based hydrocarbon oil include hydrocracked vacuum gas oil,hydrocracked atmospheric residue, hydrocracked vacuum residue, slackwax, dewaxed oil, paraffinic wax, microcrystalline wax, and petrolatum.

The first distillation step is a step of fractionating the base oilfraction and the heavy fraction from the hydrocarbon oil. Conditions ofthe fractionating step can be appropriately changed based on thecomposition of the hydrocarbon oil. For example, when the hydrocarbonoil contains 20% by volume or more of the light fraction, it ispreferred that the fractionating step is carried out by atmosphericdistillation for distilling away the light fraction from the hydrocarbonoil, and vacuum distillation for fractionating the base oil fraction andthe heavy fraction from the bottom oil of the atmospheric distillation.

The heavy fraction fractionated in the first distillation step isoffered to the hydrocracking step. The hydrocracked oil obtained in thehydrocracking step is returned to the first distillation step.

The form of a reactor used in the hydrocracking step is not particularlylimited, and a fixed-bed flow reactor filled with a hydrocrackingcatalyst is preferably used. The reactor may be a single apparatus, oran apparatus in which a plurality of reactors are arranged in series orin parallel. Moreover, a catalyst bed in the reactor may be a single bedor a plurality of beds.

A known hydrocracking catalyst is used as a hydrocracking catalyst andit is preferred to use a catalyst (hereinafter referred to as a“hydrocracking catalyst A”) in which a metal of groups 8 to 10 of theperiodic table of elements having hydrogenation activity is supported onan inorganic carrier that is a solid acid. Especially, when thehydrocarbon oil is FT synthetic oil, it is preferred to use thehydrocracking catalyst A, because there is no risk of catalyst poisoningdue to sulfur content.

Examples of the inorganic carrier that is a preferred solid acid andconstitutes the hydrocracking catalyst A include ones formed from one ormore inorganic compounds selected from zeolites, such as ultrastableY-type (USY) zeolite, Y-type zeolite, mordenite, and β-zeolite, as wellas amorphous composite metal oxides having heat resistance such assilica-alumina, silica-zirconia, and alumina-boria. Moreover, thecarrier is more preferably a composition formed from USY zeolite and oneor more amorphous composite metal oxides selected from silica-alumina,alumina-boric, and silica-zirconia, and further preferably a compositionformed from USY zeolite and alumina-boria and/or silica-alumina.

USY zeolite is one obtained by ultrastabilizing Y-type zeolite byhydrothermally treatment and/or acid treatment, in which newly poreshaving a pore diameter within a range of 2 to 10 nm are formed inaddition to the fine pore structure that Y-type zeolite inherently hasand is called micropores having a pore diameter of 2 nm or less. Theaverage particle size of the USY zeolite, which although is notespecially limited, is preferably 1.0 μm or less, and more preferably0.5 μm or less. Further, the silica/alumina molar ratio (molar ratio ofsilica based on alumina) in the USY zeolite is preferably 10 to 200,more preferably 15 to 100, and even more preferably 20 to 60.

It is preferred that the carrier of the hydrocracking catalyst Aincludes 0.1 to 80% by mass of crystalline zeolite and 0.1 to 60% bymass of amorphous composite metal oxide having heat resistance.

The carrier of the hydrocracking catalyst A can be produced by forming acarrier composition including the above-described inorganic compoundthat is a solid acid and the binder, and then calcining. It is preferredthat the blending ratio of the inorganic compound that is a solid acidis, based on the total mass of the carrier, 1 to 70% by mass, and morepreferred is 2 to 60% by mass. Further, if the carrier includes a USYzeolite, it is preferred that the blending ratio of the USY zeolite is,based on the total mass of the carrier, 0.1 to 10% by mass, and morepreferred is 0.5 to 5% by mass. Still further, if the carrier includes aUSY zeolite and alumina-boria, it is preferred that the blending ratioof the USY zeolite and the alumina-boria (USY zeolite/alumina-boria) is0.03 to 1 by mass. Moreover, if the carrier includes a USY zeolite andsilica-alumina, it is preferred that the blending ratio of the USYzeolite and the silica-alumina (USY zeolite/silica-alumina) is 0.03 to 1by mass.

Although a binder is not particularly limited, alumina, silica, titanic,and magnesia are preferable, and alumina is more preferable. The amountof the binder blended is, on the basis of the total mass of the carrier,preferably 20 to 98% by mass, and more preferably 30 to 96% by mass.

It is preferred that the temperature when calcining the carriercomposition is in the range of 400 to 550° C., more preferred is in therange of 470 to 530° C., and even more preferred is in the range of 490to 530° C. By calcining at such a temperature, sufficient solid acidityand mechanical strength can be imparted to the carrier.

Specifically, examples of a metal of groups 8 to 10 of the periodictable, which is supported by a carrier and has hydrogenation activity,include cobalt, nickel, rhodium, palladium, iridium, and platinum. Amongthem, it is preferable that metals selected from nickel, palladium, andplatinum be used singly or two or more kinds thereof be used incombination. These metals may be supported on the above-describedcarrier by a conventional method such as impregnation or ion exchange.Although there is no particular limitation on the amount of supportedmetal, it is preferred that the total amount of metal is 0.1 to 3.0% bymass based on the carrier mass. Here, the term “periodic table ofelements” refers to the long form periodic table of elements asstipulated by the IUPAC (the International Union of Pure and AppliedChemistry).

In the case of using the hydrocracking catalyst A, conditions when thebase oil fraction is made to be brought into contact with thehydrocracking catalyst A in the presence of hydrogen are notparticularly limited, and the following reaction conditions can beselected. Specifically, examples of the reaction temperature include 180to 400° C., but the reaction temperature is preferably 200 to 370° C.,more preferably 250 to 350° C., and especially preferably 280 to 350° C.If the reaction temperature is more than 400° C., not only does theyield of the base oil fraction decrease due to the base oil fractionbeing broken down into a light fraction, but the generated product iscolored, so that usage as a fuel oil base tends to be limited. On theother hand, if the reaction temperature is less than 180° C., thehydrocracking reaction does not proceed sufficiently, so that the yieldof the base oil fraction decreases. Examples of the hydrogen partialpressure include 0.5 to 12 MPa, but the hydrogen partial pressure ispreferably 1.0 to 5.0 MPa. If the hydrogen partial pressure is less than0.5 MPa, the hydrocracking tends not to proceed sufficiently. On theother hand, if the hydrogen partial pressure is more than 12 MPa, a highpressure resistance is required for the apparatus, so that equipmentcosts tend to increase. Examples of the liquid hourly space velocity(LHSV) of the heavy fraction include 0.1 to 10.0 h⁻¹, but the LHSV ispreferably 0.3 to 3.5 h⁻¹. If the LHSV is less than 0.1 h⁻¹, thehydrocracking tends to proceed excessively, and the productivity tendsto decrease. On the other hand, if the LHSV is more than 10.0 h⁻¹, thehydrocracking tends not to proceed sufficiently. Examples of thehydrogen/oil ratio include 50 to 1,000 NL/L, but the hydrogen/oil ratiois preferably 70 to 800 NL/L. If the hydrogen/oil ratio is less than 50NL/L, the hydrocracking tends not to proceed sufficiently. On the otherhand, if the hydrogen/oil ratio is more than 1,000 NL/L, large-scalehydrogen supply apparatus and the like tend to be required.

When the hydrocarbon oil is a petroleum-based hydrocarbon oil, sulfurcontent can be contained in the base oil fraction. In such a case, it ispreferred to use, as a hydrocracking catalyst, a catalyst (hereinafterreferred to as a “hydrocracking catalyst B”) having a porous inorganicoxide that includes two or more elements selected from aluminum,silicon, zirconium, boron, titanium, and magnesium, and one or moremetals selected from the elements of group 6A and group 8 of theperiodic table that are supported on the porous inorganic oxide.According to the hydrocracking catalyst B, decrease in the catalyticactivity due to sulfur poisoning is sufficiently suppressed.

As the carrier of the hydrocracking catalyst B, as described above, aporous inorganic oxide formed from two or more selected from aluminum,silicon, zirconium, boron, titanium, and magnesium can be used. Such aporous inorganic oxide is, from the perspective of enabling a muchgreater improvement in the hydrocracking activity, preferably aninorganic oxide that includes two or more selected from aluminum,silicon, zirconium, boron, titanium, and magnesium, and more preferablyan inorganic oxide (a composite oxide of an aluminum oxide and anotheroxide) that includes aluminum and another element.

If the porous inorganic oxide contains aluminum as a constituentelement, the content of aluminum is preferably 1 to 97% by mass, morepreferably 10 to 97% by mass, and even more preferably 20 to 95% by massin terms of alumina, based on the total amount of the porous inorganicoxide. If the content of aluminum is less than 1% by mass in terms ofalumina, physical properties such as the cattier acid properties are notpreferable, and a sufficient hydrocracking activity tends not to beexhibited. On the other hand, if the content of aluminum is more than97% by mass in terms of alumina, the catalyst surface area isinsufficient and the activity tends to decrease.

The method for introducing silicon, zirconium, boron, titanium, andmagnesium, which are constituent elements of the carrier other thanaluminum, into the carrier is not especially limited. A solutioncontaining these elements or the like may be used as a raw material. Forexample, there may be used, for silicon, silicon, liquid glass, andsilica sol; for boron, boric acid; for phosphorus, phosphoric acid andan alkali metal salt of phosphoric acid; for titanium, titanium sulfide,titanium tetrachloride, and various alkoxide salts; and for zirconium,zirconium sulfate and various alkoxide salts.

Further, the porous inorganic oxide preferably contains phosphorus as aconstituent element. The content of phosphorus is preferably 0.1 to 10%by mass, more preferably 0.5 to 7% by mass, and even more preferably 2to 6% by mass based on the total amount of the porous inorganic oxide.If the content of phosphorus is less than 0.1% by mass, sufficienthydrocracking activity tends not to be exhibited, and if the content ofphosphorus is more than 10% by mass, excessive cracking can proceed.

It is preferred to add the raw materials for the constituent componentsof the carrier other than the above-described aluminum oxide in a stepbefore the calcining of the carrier. For example, the raw materials areadded to an aluminum aqueous solution in advance and then an aluminumhydroxide gel containing these constituent components may be prepared orthe raw materials may be added to the prepared aluminum hydroxide gel.Alternatively, the raw materials may be added in a step in which wateror an acidic aqueous solution is added to a commercially availablealuminum oxide intermediate or a boehmite powder, and the resultingmixture is kneaded. However, it is preferred that the raw materials areallowed to coexist during the stage of preparing the aluminum hydroxidegel. Although the mechanism for exhibiting the effect of the constituentcomponents of the carrier other than aluminum oxide is not entirelyunderstood, it is thought that the constituent components form a complexoxide state with aluminum, and that this causes an increase in thecarrier surface area and interactions with the active metals to occur,thereby influencing the activity.

One or more metals selected from the elements of group 6A and group 8 ofthe periodic table is supported on the above-described porous inorganicoxide acting as a carrier. Among these metals, it is preferred to use acombination of two or more metals selected from cobalt, molybdenum,nickel, and tungsten. Examples of preferred combinations includecobalt-molybdenum, nickel-molybdenum, nickel-cobalt-molybdenum, andnickel-tungsten. Among these, more preferred is a combination ofnickel-molybdenum, nickel-cobalt-molybdenum, and nickel-tungsten. Duringthe hydrocracking, these metals are converted into a sulfide state touse.

As the content of the active metal based on the catalyst mass, the rangeof the total amount of tungsten and molybdenum supported is preferably12 to 35% by mass, and more preferably 15 to 30% by mass, in terms ofthe oxide. If the total amount of tungsten and molybdenum supported isless than 12% by mass, the active sites decrease and sufficient activitytends not to be obtained. On the other hand, if the total amount oftungsten and molybdenum supported is more than 35% by mass, the metalsare not effectively dispersed and sufficient activity tends not to beobtained. The range of the total amount of cobalt and nickel supportedis preferably 1.0 to 15% by mass and more preferably 1.5 to 12% by massin terms of the oxide. If the total amount of cobalt and nickelsupported is less than 1.0% by mass, a sufficient co-catalyst effect isnot obtained and the activity tends to decrease. On the other hand, ifthe total amount of cobalt and nickel supported is more than 15% bymass, the metals are not effectively dispersed and sufficient activitytends not to be obtained.

The method for incorporating these active metals into the catalyst isnot especially limited. A known method that is applied when producing ageneral hydrocracking catalyst may be employed. Generally, it ispreferred to employ a method in which a solution containing a salt ofthe active metal is impregnated into the catalyst carrier. In addition,an equilibrium adsorption method, a pore-filling method, anincipient-wetness method and the like can also be preferably employed.For example, a pore-filling method is a method in which the pore volumeof a carrier is measured in advance and then the carrier is impregnatedwith the same volume of a metal salt solution. In addition, theimpregnation method is not especially limited. The carrier may beimpregnated by a suitable method based on the amount of the metalsupported and the physical properties of the catalyst carrier.

In the present embodiment, the number of the hydrocracking catalyst Btypes to be used is not especially limited. For example, one type ofcatalyst may be used singly or a plurality of catalysts with differentactive metal species or carrier constituent components may be used.Examples of a suitable combination when using a plurality of differentcatalysts include a catalyst containing cobalt-molybdenum following onfrom a catalyst containing nickel-molybdenum, a catalyst containingnickel-cobalt-molybdenum following on from a catalyst containingnickel-molybdenum, a catalyst containing nickel-cobalt-molybdenumfollowing on from a catalyst containing nickel-tungsten, and a catalystcontaining cobalt-molybdenum following on from a catalyst containingnickel-cobalt-molybdenum. Prior to and/or following these combinations,a nickel-molybdenum catalyst may be further combined.

When combining a plurality of catalysts with different carriercomponents, a catalyst may be used that, for example, has an aluminumoxide content in the range of 80 to 99% by mass following on from acatalyst having an aluminum oxide content of 30% by mass or more andless than 80% by mass based on the total mass of the carrier.

Further, other than the hydrocracking catalyst B, a guard catalyst, ademetallization catalyst, and an inactive filler may optionally be usedfor the purpose of trapping the scale content which flows in along withthe base oil fraction and supporting the hydrocracking catalyst B at thepartition part of the catalyst bed as necessary. These may be usedsingly or in combinations thereof.

It is preferred that the pore volume of the hydrocracking catalyst B asmeasured by a nitrogen adsorption BET method is 0.30 to 0.85 ml/g, andmore preferred is 0.45 to 0.80 ml/g. If the pore volume is less than0.30 ml/g, the dispersibility of the supported metals is insufficient,and the active sites may decrease. In addition, if the pore volume ismore than 0.85 ml/g, the catalyst strength is insufficient, so that thecatalyst may turn into a powder and break up during use.

Further, it is preferred that the average pore size of the catalystdetermined by a nitrogen adsorption BET method is 5 to 11 nm, and morepreferred is 6 to 9 nm. If the average pore size is less than 5 nm, thereaction substrate is not sufficiently dispersed in the pores, and thereactivity may decrease. In addition, if the average pore size is morethan 11 nm, the pore surface area decreases and the activity may becomeinsufficient.

In addition, in the hydrocracking catalyst B, in order to maintaineffective catalyst pores and exhibit sufficient activity, it ispreferred that the ratio of the pore volume derived from pores having apore diameter of 3 nm or less to the total pore volume is 35% by volumeor less.

When the hydrocracking catalyst B is used, the hydrocracking conditionscan be set to, for example, a hydrogen pressure of 2 to 13 MPa, a liquidhourly space velocity (LHSV) of 0.1 to 3.0 h⁻¹, and a hydrogen-oil ratio(hydrogen/oil ratio) of 150 to 1,500 NL/L, are preferably a hydrogenpressure of 4.5 to 12 MPa, a liquid hourly space velocity of 0.3 to 1.5h⁻¹, and a hydrogen-oil ratio of 380 to 1,200 NL/L, and more preferablya hydrogen pressure of 6 to 15 MPa, a liquid hourly space velocity of0.3 to 1.5 h⁻¹, and a hydrogen-oil ratio of 350 to 1,000 NL/L. All ofthese conditions are factors having an influence on the reactionactivity. For example, if the hydrogen pressure and the hydrogen-oilratio are less than the above lower limits, the reactivity tends todecrease and the activity tends to rapidly decrease. On the other hand,if the hydrogen pressure and the hydrogen-oil ratio are more than theabove upper limits, an excessive investment in equipment such as acompressor tends to be required. In addition, the lower the liquidhourly space velocity is, the more advantageous it tends to be for thereaction. However, if the liquid hourly space velocity is less than theabove lower limit, a reactor having an extremely large internal volumeis required and an excessive investment in equipment tends to berequired. On the other hand, if the liquid hourly space velocity is morethan the above upper limit, the reaction tends not to sufficientlyproceed. Further, the reaction temperature may be 180 to 400° C., ispreferably 200 to 370° C., more preferably 250 to 350° C., andespecially preferably 280 to 350° C. If the reaction temperature is morethan 400° C., not only does the yield of the base oil fraction decreasedue to the base oil fraction being broken down into a light fraction,but the generated product is colored, so that usage as a fuel oil basetends to be limited. On the other hand, if the reaction temperature isless than 180° C., the hydrocracking reaction does not proceedsufficiently, so that the yield of the base oil fraction decreases.

In the hydrocracking step, the heavy fraction is, due to thehydrocracking, converted into hydrocarbons having a boiling point ofabout 520° C. or less. On the other hand, a part of the heavy fractionis not sufficiently hydrocracked, and remains as an uncracked heavyfraction having a boiling point of 520° C. or more.

The composition of the hydrocracked oil is determined based on thehydrocracking catalyst to be used and the hydrocracking reactionconditions. Here, unless otherwise stated, the “hydrocracked oil” refersto all the products of hydrocracking, including the uncracked heavyfraction. If the hydrocracking reaction conditions are severer thannecessary, although the content of the uncracked heavy fraction in thehydrocracked oil decreases, a light fraction having a boiling point of340° C. or less increases, and the yield of the preferred base oilfraction (340 to 520° C. fraction) decreases. On the other hand, if thehydrocracking reaction conditions are milder than necessary, the contentof the uncracked heavy fraction increases, and the base oil fractionyield decreases. In the case where the ratio M2/M1 of the mass M2 of thecracking products having a boiling point of 25 to 520° C. to the mass M1of all the cracking products having a boiling point of 25° C. or more isreferred to as a “cracking ratio”, generally, the reaction conditionsare preferably selected such that the cracking ratio M2/M1 is 5 to 70%,preferably 10 to 60%, and further preferably 20 to 50%.

Next, the dewaxing step will be described. In the dewaxing step, thebase oil fraction fractionated in the first distillation step is broughtinto contact with a hydrocracking catalyst in the presence of hydrogen(molecular hydrogen). Accordingly, the base oil fraction is dewaxed byhydroisomerization to obtain a dewaxed oil.

As a tube reactor for the dewaxing step, a known fixed-bed tube reactorcan be used. More specifically, for example, hydroisomerization can beperformed by filling a fixed-bed flow reactor with a hydroisomerizationcatalyst and making hydrogen (molecular hydrogen) and the base oilfraction flow through the reactor.

As the hydroisomerization catalyst, a catalyst that is generally usedfor hydroisomerization, namely, a catalyst in which a metal having ahydrogenation activity is supported on an inorganic carrier, can beused.

As the metal having a hydrogenation activity and constituting thehydroisomerization catalyst, one or more metals selected from the groupconsisting of metals of group 6, group 8, group 9, and group 10 of theperiodic table of elements are used. Specific examples of these metalsinclude noble metals such as platinum, palladium, rhodium, ruthenium,iridium, and osmium, or cobalt, nickel, molybdenum, tungsten, and iron.Preferred are platinum, palladium, nickel, cobalt, molybdenum, andtungsten, and more preferred are platinum and palladium. In addition, itis also preferred to use these metals in combinations of a plurality ofspecies. In this case, examples of preferred combinations includeplatinum-palladium, cobalt-molybdenum, nickel-molybdenum,nickel-cobalt-molybdenum, and nickel-tungsten.

Examples of inorganic carriers constituting the hydroisomerizationcatalyst include metal oxides such as alumina, silica, titania,zirconia, and boric. These metal oxides may be one kind, a mixture oftwo or more kinds, or a composite metal oxide such as silica-alumina,silica-zirconia, alumina-zirconia, and alumina-boria. From theperspective of efficiently promoting the hydroisomerization of normalparaffins, the inorganic carrier is preferably a composite metal oxidethat is a solid acid, such as silica-alumina, silica-zirconia,alumina-zirconia, and alumina-boria. Further, a small amount of zeolitemay be included in the inorganic carrier. In order to improve themoldability and mechanical strength of the carrier, the inorganiccarrier may be blended with a binder. Examples of preferred bindersinclude alumina, silica, and magnesia.

As the content of the metal having a hydrogenation activity in thehydroisomerization catalyst, if this metal is the above-described noblemetal, it is preferred that the content is about 0.1 to 3% by mass basedon the mass of the carrier as metal atoms. Further, if this metal is ametal other than the above-described noble metals, it is preferred thatthe content is about 2 to 50% by mass based on the mass of the carrieras a metal oxide. If the content of the metal having a hydrogenationactivity is less than the above-described lower limit, hydrorefining andhydroisomerization tend not to proceed sufficiently. On the other hand,if the content of the metal having a hydrogenation activity is more thanthe above-described upper limit, dispersion of the metal having ahydrogenation activity deteriorates, so that the activity of thecatalyst tends to decrease, and the catalyst cost increases.

Further, the hydroisomerization catalyst may be a catalyst in which oneor more metals selected from the elements of group 8 of the periodictable that is supported on a carrier including a porous inorganic oxidethat is formed from a substance selected from aluminum, silicon,zirconium, boron, titanium, magnesium, and zeolite.

Examples of the porous inorganic oxide used as a carrier of such ahydroisomerization catalyst include alumina, titania, zirconia, boria,silica, or zeolite, and of these, preferred is a porous inorganic oxideformed from alumina and at least one of titania, zirconia, boria,silica, and zeolite. The production method is not especially limited,but an arbitrary preparation method may be employed that uses rawmaterials in the form of various sols or salt compounds corresponding tothe respective elements. Furthermore, the carrier may be prepared byonce preparing a composite hydroxide or a composite oxide, such assilica-alumina, silica-zirconia, alumina-titania, silica-titania, andalumina-boria, and then adding the composite hydroxide or compositeoxide in the form of an alumina gel or other hydroxide, or in the forman appropriate solution, at an arbitrary stage of the preparation step.The proportion of alumina to the other oxide may be any ratio based onthe carrier, but the content of alumina is preferably 90% by mass orless, more preferably 60% by mass or less, even more preferably 40% bymass or less, and preferably 10% by mass or more, and more preferably20% by mass or more.

Examples of the zeolite, which is a crystalline alumino silicate,include faujasite, pentasil, mordenite, TON, MTT, and MRE. A zeolitethat has been ultrastabilized by a predetermined hydrothermal treatmentand/or acid treatment, or a zeolite whose alumina content has beenadjusted may be used. It is preferred to use faujasite or mordenite, andespecially preferred to use a Y or beta type. The Y type is preferablyultrastabilized. A zeolite ultrastabilized by a hydrothermal treatmenthas, in addition to its inherent pore structure, called micropores, of20 angstroms or less, newly formed pores in the range of 20 to 100angstroms. The hydrothermal treatment may be carried out under knownconditions.

As the active metal of such a hydroisomerization catalyst, one or moremetals selected from the elements of group 8 of the periodic table canbe used. Among these metals, preferably used are one or more metalsselected from Pd, Pt, Rh, Ir, Au and Ni, and more preferably used is acombination thereof. Examples of a preferred combination include Pd—Pt,Pd—Ir, Pd—Rh, Pd—Au, Pd—Ni, Pt—Rh, Pt—Ir, Pt—Au, Pt—Ni, Rh—Ir, Rh—Au,Rh—Ni, Ir—Au, Ir—Ni, Au—Ni, Pd—Pt—Rh, Pd—Pt—Ir, and Pt—Pd—Ni. Amongthese, more preferred combinations are Pd—Pt, Pd—Ni, Pt—Ni, Pd—Ir,Pt—Rh, Pt—Ir, Rh—Ir, Pd—Pt—Rh, Pd—Pt—Ni, and Pd—Pt—Ir, and even morepreferred combinations are Pd—Pt, Pd—Ni, Pt—Ni, Pd—Ir, Pt—Ir, Pd—Pt—Ni,and Pd—Pt—Ir.

The total content of the active metals is preferably 0.1 to 2% by mass,more preferably 0.2 to 1.5% by mass, and even more preferably 0.5 to1.3% by mass, in terms of metal, based on catalyst mass. If the totalamount of metals supported is less than 0.1% by mass, the number ofactive sites is reduced, so that sufficient activity tends not to beobtained. On the other hand, if the total amount of metals supported ismore than 2% by mass, the metals are not dispersed effectively, so thatsufficient activity tends not to be obtained.

For any of the above-described hydroisomerization catalysts, the methodfor supporting the active metal on the carrier is not especiallylimited. A known method that is applied when producing a generalhydroisomerization catalyst may be employed. Generally, it is preferredto employ a method in which a solution containing a salt of the activemetal is impregnated into the catalyst carrier. In addition, anequilibrium adsorption method, a pore-filling method, anincipient-wetness method and the like can also be preferably employed.For example, a pore-filling method is a method in which the pore volumeof a carrier is measured in advance and then the carrier is impregnatedwith the same volume of a metal salt solution. Although the impregnationmethod is not especially limited, the carrier may be impregnated by asuitable method based on the amount of the metal supported and thephysical properties of the catalyst carrier.

As the hydroisomerization catalyst, the following catalyst can also beused.

<Specific Aspect of the Hydroisomerization Catalyst>

The hydroisomerization catalyst according to this aspect is impartedwith its characteristics as a result of being produced by a specificmethod. The hydroisomerization catalyst according to the present aspectwill now be described with reference to a preferred production aspectthereof.

The method for producing the hydroisomerization catalyst according tothe present aspect includes a first step of obtaining a carrierprecursor by heating a mixture that includes an ion-exchanged zeoliteobtained by ion-exchanging an organic template-containing zeolite thatcontains an organic template and has a one-dimensional, 10-membered ringpore structure in a solution containing ammonium ions and/or protons,and a binder, in a N₂ atmosphere at a temperature of 250 to 300° C., anda second step of obtaining a hydroisomerization catalyst in whichplatinum and/or palladium is supported on a carrier including zeolite bycalcining a catalyst precursor incorporating a platinum salt and/orpalladium salt in the carrier precursor in an atmosphere containingmolecular oxygen at a temperature of 350 to 400° C.

From the perspective of achieving a high level of both highisomerization activity and suppressed cracking activity in thehydroisomerization reactions of normal paraffins, the organictemplate-containing zeolite used in the present aspect has aone-dimensional pore structure formed from a 10-membered ring. Examplesof such zeolites include AEL, EUO, FER, NFU, MEL, WI, NES, TON, MTT,WEI, *MRE, and SSZ-32. The above three-lettered acronyms representframework-type codes assigned to various structures of classifiedmolecular sieve-type zeolites by the Structure Commission of theInternational Zeolite Association. It is also noted that zeolites havingthe same topology are collectively designated by the same code.

Among the above-described zeolites having a one-dimensional, 10-memberedring pore structure, from the perspective of high isomerization activityand low cracking activity, preferred as the organic template-containingzeolite are zeolites having a TON or an MIT structure, zeolite ZSM-48,which is a zeolite having a *MRE structure, and zeolite SSZ-32. ZeoliteZSM-22 is more preferred among zeolites having the TON structure, andzeolite ZSM-23 is more preferred among zeolites having the MTTstructure.

The organic template-containing zeolite is hydrothermally synthesizedaccording to a known method from a silica source, an alumina source, andan organic template that is added to build the above-describedpredetermined pore structure.

The organic template is an organic compound having an amino group, anammonium group and the like, and is selected according to the structureof the zeolite to be synthesized. However, it is preferred that theorganic template is an amine derivative. Specifically, the organictemplate is preferably at least one selected from the group consistingof alkylamines, alkyldiamines, alkyltriamines, alkyltetramines,pyrrolidine, piperazine, aminopiperazine, alkylpentamines,alkylhexamines, and their derivatives.

The molar ratio of the silicon element to aluminum element ([Si]/[Al];hereinafter referred to as a “Si/Al ratio”) that constitute the organictemplate-containing zeolite having a one-dimensional, 10-membered ringpore structure is preferably 10 to 400, and more preferably 20 to 350.If the Si/Al ratio is less than 10, although the activity for theconversion of normal paraffins increases, the isomerization selectivityto isoparaffins decreases, and cracking reactions caused by an increasein the reaction temperature tend to sharply increase, which isundesirable. Conversely, if the Si/Al ratio is more than 400, thecatalytic activity needed for the conversion of normal paraffins cannotbe easily obtained, which is undesirable.

The synthesized organic template-containing zeolite, which haspreferably been washed and dried, typically has alkali metal cations ascounter cations, and incorporates the organic template in its porestructure. The zeolite containing an organic template, which is used forproducing the hydroisomerization catalyst according to the presentinvention, is preferably in such a synthesized state, i.e., preferably,the zeolite has not been subjected to a calcining treatment for removingthe organic template incorporated therein.

The organic template-containing zeolite is next ion-exchanged in asolution containing ammonium ions and/or protons. By the ion-exchangetreatment, the counter cations contained in the organictemplate-containing zeolite are exchanged for ammonium ions and/orprotons. Further, at the same time, a portion of the organic templateincorporated in the organic template-containing zeolite is removed.

The solution used for the ion-exchange treatment is preferably asolution that uses a solvent containing at least 50% by volume of water,and more preferably is an aqueous solution. Examples of compounds forsupplying ammonium ions into the solution include various inorganic andorganic ammonium salts, such as ammonium chloride, ammonium sulfate,ammonium nitrate, ammonium phosphate, and ammonium acetate. On the otherhand, mineral acids such as hydrochloric acid, sulfuric acid, and nitricacid are typically used as compounds for supplying protons into thesolution. The ion-exchanged zeolite (here, an ammonium-form zeolite)obtained by ion exchange of the organic template-containing zeolite inthe presence of ammonium ions releases ammonia during subsequentcalcination, and the counter cations are converted into protons to formBronsted acid sites. Ammonium ions are preferred as the cationic speciesused for the ion exchange. The amount of ammonium ions and/or protonscontained in the solution is preferably set to 10 to 1,000 equivalentsbased on the total amount of the counter cations and organic templatecontained in the organic template-containing zeolite used.

The ion-exchange treatment may be performed on the organictemplate-containing zeolite simple substance in powder form, oralternatively, prior to the ion-exchange treatment, the organictemplate-containing zeolite may be blended with an inorganic oxide,which is a binder, and molded, and the ion-exchange treatment may beperformed on the resulting molded body. However, if the molded body issubjected to the ion-exchange treatment in an uncalcined state, problemssuch as the molded body collapsing and turning into a powder tend tooccur. Therefore, it is preferred to subject the organictemplate-containing zeolite in powder form to an ion-exchange treatment.

The ion-exchange treatment is preferably performed based on a standardmethod, i.e., a method in which the zeolite containing an organictemplate is dipped in a solution, preferably an aqueous solution,containing ammonium ions and/or protons, and the solution is stirred orfluidized. It is preferred to perform the stirring or fluidization underheating to increase the ion-exchange efficiency. In the present aspect,especially preferred is a method in which the aqueous solution isheated, boiled, and ion-exchanged under reflux.

Further, from the perspective of increasing the ion-exchange efficiency,during the ion exchange of the zeolite in a solution, it is preferred toexchange the solution with a fresh one once or twice or more, and morepreferably exchanged with a fresh one once or twice. When exchanging thesolution once, the ion-exchange efficiency can be improved by, forexample, dipping the organic template-containing zeolite in a solutioncontaining ammonium ions and/or protons, and heating the solution underreflux for 1 to 6 hours, followed by exchanging the solution with afresh one, and further heating under reflux for 6 to 12 hours.

By the ion-exchange treatment, substantially all of the counter cationssuch as an alkali metal in the zeolite can be exchanged for ammoniumions and/or protons. On the other hand, regarding the organic templateincorporated in the zeolite, although a portion of the organic templateis removed by the ion-exchange treatment, it is generally difficult toremove all of the organic template even if the ion-exchange treatment isrepeatedly performed, so that a portion of the organic template remainsinside the zeolite.

In the present aspect, a carrier precursor is obtained by heating amixture in which the ion-exchanged zeolite and the binder are includedin a nitrogen atmosphere at a temperature of 250 to 350° C.

The mixture in which the ion-exchanged zeolite and the binder areincluded is preferably obtained by blending an inorganic oxide, which isa binder, with the ion-exchanged zeolite obtained by the above-describedmethod, and molding the resulting composition to form a molded body. Thepurpose of blending an inorganic oxide with the ion-exchanged zeolite isto increase the mechanical strength of the carrier (in particular, aparticulate carrier) obtained by calcining the molded body to a degreethat can withstand practical applications. However, the present inventorfound that the selection of the type of inorganic oxide affects theisomerization selectivity of the hydroisomerization catalyst. From thisperspective, at least one inorganic oxide selected from alumina, silica,titania, boria, zirconia, magnesia, ceria, zinc oxide, phosphorus oxide,and a composite oxide containing a combination of two or more of theseoxides can be used as the inorganic oxide. Among the above, silica andalumina are preferred, and alumina is more preferred, from theperspective of further improving the isomerization selectivity of thehydroisomerization catalyst. The phrase “composite oxide containing acombination of two or more of these oxides” refers to a composite oxidecontaining at least two components from alumina, silica, titania, boria,zirconia, magnesia, ceria, zinc oxide, and phosphorus oxide, but ispreferably an alumina-based composite oxide containing 50% by mass ormore of an alumina component based on the composite oxide, and amongthose, is more preferably alumina-silica.

The blending ratio of the ion-exchanged zeolite and the inorganic oxidein the above-described composition is preferably 10:90 to 90:10, andmore preferably 30:70 to 85:15, in terms of the mass ratio of theion-exchanged zeolite to the inorganic oxide. If this ratio is less than10:90, the activity of the hydroisomerization catalyst tends to beinsufficient, which is undesirable. Conversely, if the ratio is morethan 90:10, the mechanical strength of the carrier obtained by moldingand calcining the composition tends to be insufficient, which isundesirable.

Although the method for blending the inorganic oxide with theion-exchanged zeolite is not especially limited, a general method can beemployed, such as, for example, a method in which a suitable amount of aliquid such as water is added to the powders of both components to forma viscous fluid, and the fluid is kneaded in a kneader or the like.

The composition containing the ion-exchanged zeolite and inorganicoxide, or a viscous fluid including the composition, is molded by amethod such as extrusion molding, and is preferably dried, to form aparticulate molded body. Although the shape of the molded body is notespecially limited, examples of the shape include a cylindrical shape, apellet shape, a spherical shape, and an irregular tubular shape having athree leaf shaped or a four leaf shaped cross-section. Although the sizeof the molded body is not especially limited, the molded body ispreferably, for example, about 1 to 30 mm in the long axis, and about 1to 20 mm in the short axis, from the perspective of the ease ofhandling, the load density in the reactor and the like.

In the present aspect, it is preferred to form the carrier precursor byheating the thus-obtained molded body in a N₂ atmosphere at atemperature of 250 to 350° C. Regarding the heating time, preferred is0.5 to 10 hours, and more preferred is 1 to 5 hours.

In the present aspect, if the above-described heating temperature isless than 250° C., a large amount of organic template remains, and thezeolite pores become blocked with the remaining template. Theisomerization active sites are thought to exist near the pore mouth.Thus, in the above case, the reaction substrate cannot disperse into thepores due to the pore blockage, so that the active sites become covered,the isomerization reaction does not easily proceed, and a normalparaffin conversion rate tends not to be sufficiently obtained. On theother hand, if the heating temperature is more than 350° C., theisomerization selectivity of the obtained isomerization catalyst doesnot sufficiently improve.

It is preferred that the lower limit for the temperature when formingthe carrier precursor by heating the molded body is 280° C. or more, andthat the upper limit for the temperature is 330° C. or less.

In the present aspect, it is preferred to heat the above-describedmixture so that a portion of the organic template included in the moldedbody remains. Specifically, it is preferred to set the heatingconditions so that the micropore volume per unit mass of thehydroisomerization catalyst obtained by calcining after thebelow-described metal supporting is 0.02 to 0.11 cc/g, and the microporevolume per unit mass of the zeolite that is contained in that catalystis 0.04 to 0.12 cc/g.

Next, the catalyst precursor incorporating a platinum salt and/orpalladium salt in the above-described carrier precursor is calcined inan atmosphere containing molecular oxygen at a temperature of 350 to400° C., preferably 380 to 400° C., and more preferably 400° C., toobtain a hydroisomerization catalyst in which a platinum and/orpalladium is supported on a carrier including zeolite. Here, “in anatmosphere containing molecular oxygen” means bringing into contact witha gas including oxygen gas, and of those preferably air. The calciningtime is preferably 0.5 to 10 hours, and more preferably 1 to 5 hours.

Examples of the platinum salt include chloroplatinic acid,tetraammineplatinum dinitrate, dinitroaminoplatinum, andtetraamminedichloroplatinum. Since chloride salts can producehydrochloric acid during a reaction, which may cause apparatuscorrosion, tetraammineplatinum dinitrate, which is a platinum salt thatis not a chloride salt and in which a high level of platinum isdispersed, is preferred.

Examples of the palladium salt include palladium chloride tetraamminepalladium nitrate, and diaminopalladium nitrate. Since chloride saltscan produce hydrochloric acid during a reaction, which may causeapparatus corrosion, tetraammine palladium nitrate, which is a palladiumsalt that is not a chloride salt and in which a high level of palladiumis dispersed, is preferred.

The amount of the active metal supported on the carrier includingzeolite according to the present aspect is preferably 0.001 to 20% bymass, and more preferably 0.01 to 5% by mass, based on the mass of thecarrier. If the amount supported is less than 0.001% by mass, it isdifficult to impart a predetermined hydrogenation/dehydrogenationfunction to the catalyst. Conversely, if the amount supported is morethan 20% by mass, conversion on the active metal of hydrocarbons intolighter products by cracking tends to proceed, so that the yield of theintended fraction tends to decrease, and the catalyst costs tend toincrease, which are undesirable.

Further, when the hydroisomerization catalyst according to the presentaspect is used for hydroisomerization of a hydrocarbon oil containingmany sulfur-containing compounds and/or nitrogen-containing compounds,from the perspective of the durability of catalytic activity, it ispreferred that the active metals are a combination such asnickel-cobalt, nickel-molybdenum, cobalt-molybdenum,nickel-molybdenum-cobalt, or nickel-tungsten-cobalt. It is preferredthat the amount of these metals supported is 0.001 to 50% by mass, andmore preferably 0.01 to 30% by mass, based on the mass of the carrier.

In the present aspect, it is preferred to calcine the above-describedcatalyst precursor so that the organic template remaining in the carrierprecursor remains. Specifically, it is preferred to set the heatingconditions so that the micropore volume per unit mass of the obtainedhydroisomerization catalyst is 0.02 to 0.11 cc/g, and the microporevolume per unit mass of the zeolite that is contained in that catalystis 0.04 to 0.12 cc/g.

The micropore volume per unit mass of the hydroisomerization catalyst iscalculated by a method called nitrogen adsorption measurement. Namely,for the catalyst, the micropore volume per unit mass of the catalyst iscalculated by analyzing a physical adsorption and desorption isotherm ofnitrogen measured at the temperature of liquid nitrogen (−196° C.),specifically, analyzing an adsorption isotherm of nitrogen measured atthe temperature of liquid nitrogen (−196° C.) by a t-plot method.Further, the micropore volume per unit mass of the zeolite contained inthe catalyst is also calculated by the above-described nitrogenadsorption measurement.

In addition, in the present description, a micropore indicates a “porehaving a diameter of 2 nm or less” defined in IUPAC (International Unionof Pure and Applied Chemistry).

A micropore volume V_(z) per unit mass of the zeolite contained in thecatalyst can be calculated, for example, if the binder does not have amicropore volume, based on the following expression from a value V_(c)of the micropore volume per unit mass of the hydroisomerization catalystand the content M_(z) (% by mass) of zeolite in the catalyst.

V _(z) =V _(c) /M _(z)×100

It is preferred that, subsequent to the calcination treatment, thehydroisomerization catalyst of the present aspect is subjected to areduction treatment after the catalyst is loaded in the reactor forconducting the hydroisomerization reaction. Specifically, it ispreferred that the hydroisomerization catalyst is subjected to thereduction treatment for about 0.5 to 5 hours in an atmosphere containingmolecular hydrogen, and preferably under a stream of hydrogen gas,preferably at 250 to 500° C., and more preferably at 300 to 400° C. Byperforming this step, it can be further ensured that high activity forthe dewaxing of the hydrocarbon oil can be imparted to the catalyst.

The hydroisomerization catalyst according to the present aspect is ahydroisomerization catalyst containing a carrier that includes a zeolitehaving a one-dimensional, 10-membered ring pore structure and a binder,and platinum and/or palladium supported on the carrier, in which themicropore volume per unit mass of the catalyst is 0.02 to 0.11 cc/g.Further, this zeolite is preferably a zeolite derived from ion-exchangedzeolite obtained by ion-exchanging an organic template-containingzeolite that contains an organic template and has a one-dimensional,10-membered ring pore structure in a solution containing ammonium ionsand/or protons, in which the micropore volume per unit mass of thezeolite contained in the catalyst is 0.04 to 0.12 cc/g.

The above-described hydroisomerization catalyst can be produced by themethod described above. The micropore volume per unit mass of thecatalyst and the micropore volume per unit mass of the zeolite containedin the catalyst can be set to be within the above-described ranges byappropriately adjusting the amount of ion-exchanged zeolite blended inthe mixture including the ion-exchanged zeolite and a binder, theheating conditions of the mixture in a N₂ atmosphere, and the heatingconditions of the catalyst precursor in the atmosphere containingmolecular oxygen.

The reaction temperature in the dewaxing step is preferably 200 to 450°C., and more preferably 220 to 400° C. If the reaction temperature isless than 200° C., the isomerization of the normal paraffins containedin the base oil fraction tends not to easily proceed, so that thereduction and removal of the wax component tend to be insufficient.Conversely, if the reaction temperature is more than 450° C., crackingof the base oil fraction is significant, so that the yield of thelubricant base oil tends to decrease.

The reaction pressure in the dewaxing step is preferably 0.1 to 20 MPa,and more preferably 0.5 to 15 MPa. If the reaction pressure is less than0.1 MPa, catalyst degradation due to the formation of coke tends to beaccelerated. Conversely, if the reaction pressure is more than 20 MPa,construction costs for the apparatus increase, so that it tends tobecome difficult to realize an economical process.

In the dewaxing step, the liquid hourly space velocity of the base oilfraction based on the catalyst is preferably 0.01 to 100 hr⁻¹, and morepreferably 0.1 to 50 hr¹. If the liquid hourly space velocity is lessthan 0.01 hr⁻¹, the cracking of the base oil fraction tends to proceedexcessively, so that production efficiency tends to decrease.Conversely, if the liquid hourly space velocity is more than 100 hr⁻¹,the isomerization of the normal paraffins contained in the base oilfraction tends not to proceed easily, so that the reduction and removalof the wax component tend to be insufficient.

The supply ratio of hydrogen to base oil fraction is preferably 100 to1,000 Nm³/m³, and more preferably 200 to 800 Nm³/m³. If the supply ratiois less than 100 Nm³/m³, for example, when the base oil fractioncontains sulfur or nitrogen content, hydrogen sulfide and ammonia gasproduced by desulfurization and denitrification reactions that accompanythe isomerization reaction are adsorbed onto and poison the active metalon the catalyst, which tends to make it difficult to achieve apredetermined catalytic performance. Conversely, if the supply ratio ismore than 1,000 Nm³/m³, hydrogen supply equipment having an increasedcapacity is required, which tends to make it difficult to realize aneconomical process.

The dewaxed oil obtained in the dewaxing step is offered to thehydrofinishing step, and hydrofinishing treatment (hydrorefiningtreatment) is performed.

A reactor used in the hydrofinishing step is not particularly limited,and the hydrofinishing treatment (hydrorefining treatment) can besuitably performed by filling a fixed-bed flow reactor with apredetermined hydrorefining catalyst and making molecular hydrogen andthe above-described dewaxed oil flow through the reactor. Thehydrofinishing treatment (hydrorefining treatment) described in thepresent invention means improvement in oxidation stability and a hue ofthe lubricant oil, and olefin hydrogenation and aromatic hydrogenationof the dewaxed oil are performed.

Examples of the hydrorefining catalyst include catalysts that include acarrier including one or more inorganic solid acidic substances selectedfrom alumina, silica, zirconia, titania, boria, magnesia, andphosphorus, and one or more active metals selected from the groupconsisting of platinum, palladium, nickel-molybdenum, nickel-tungsten,and nickel-cobalt-molybdenum that is supported on the carrier.

A preferred carrier is an inorganic solid acidic substance that includesat least two or more of alumina, silica, zirconia, or titania.

As the method for supporting the active metals on the carrier, aconventional method such as impregnation or ion exchange may beemployed.

The amount of the active metals supported in the hydrorefining catalystis preferably such that the total amount of metal is 0.1 to 25% by massbased on the carrier.

The average pore size of the hydrorefining catalyst is preferably 6 to60 nm, and more preferably 7 to 30 nm. If the average pore size is lessthan 6 nm, a sufficient catalytic activity tends not to be obtained,while if the average pore size is more than 60 nm, catalytic activitytends to decrease due to a decrease in the level of dispersion of theactive metals. Further, it is preferred that the pore volume of thehydrorefining catalyst is 0.2 mL/g or more. If the pore volume is lessthan 0.2 mL/g, degradation of the activity of the catalyst tends tooccur earlier. In addition, it is preferred that the specific surfacearea of the hydrorefining catalyst is 200 m²/g or more. If the specificsurface area of the catalyst is less than 200 m²/g, the dispersibilityof the active metals is insufficient, so that activity tends todecrease. The pore volume and the specific surface area of the catalystcan be measured and calculated by a BET method using nitrogenadsorption.

It is preferred that the reaction conditions in the hydrofinishing stepare set to a reaction temperature of 200 to 300° C., a hydrogen partialpressure of 3 to 20 MPa, an LHSV of 0.5 to 5 h-1, and a hydrogen/oilratio of 1000 to 5000 scfb, and more preferred are a reactiontemperature of 200° C. to 300° C., a hydrogen partial pressure of 4 to18 MPa, an LHSV of 0.5 to 4 h-1, and a hydrogen/oil ratio of 2000 to5000 scfb.

In the present embodiment, it is preferred to adjust the reactionconditions so that the sulfur and nitrogen content in the hydrorefinedoil is 5 ppm by mass or less and 1 ppm by mass or less, respectively.

The refined oil obtained by the hydrofinishing step is offered to thesecond fractionating step. Then, a desired lubricant oil fraction isobtained by setting a plurality of cut points and performing vacuumdistillation of the hydrorefined oil.

In addition, the hydrorefined oil may contain light fractions such asnaphtha and kerosene and gas oil produced as a byproduct by thehydroisomerization and the hydrofinishing treatment (hydrorefiningtreatment), and these light fractions can be collected as a fractionhaving a boiling point of 350° C. or less, for example.

The method for producing a lubricant base oil of the present inventionis not limited to the above-described embodiments, and can beappropriately changed. For example, the method for producing a lubricantbase oil of the present invention may include a distillation step ofobtaining a lubricant oil fraction by fractionating the dewaxed oilobtained by the above-described producing method of the dewaxed oil, anda hydrofinishing step of performing hydrofinishing treatment(hydrorefining treatment) of the lubricant oil fraction obtained thedistillation step.

The lubricant base oils according to the above-described first to thirdembodiments and the lubricant base oil obtained by the production methodaccording to the fourth embodiment excel in a low-temperature viscositycharacteristic and a sealing property, and can be suitably used aslubricant base oils for various applications. Specifically, examples ofthe applications of the lubricant base oil include lubricant oils usedfor internal combustion engines such as passenger vehicle gasolineengines, two-wheel vehicle gasoline engines, diesel engines, gasengines, gas heat pump engines, marine engines, and power-generatingengines (internal combustion engine lubricant oil), lubricant oils usedfor driving transmission devices such as automatic transmissions, manualtransmissions, non-stage transmissions, and final reduction gears(driving transmission device oil), hydraulic oils used for hydraulicsystems such as dampers and construction machines, compressor oils,turbine oils, industrial gear oils, refrigerant oils, rust preventingoils, heating medium oils, gas holder seal oils, bearing oils, papermachine oils, machine tool oils, sliding guide surface oils, electricalinsulating oils, cutting oils, press oils, rolling oils, and heattreating oils, and by using the lubricant base oil according to thepresent embodiment for these applications, both a low-temperatureviscosity characteristic and a sealing property can be satisfied at ahigh level.

In the above-described applications, the lubricant base oil according toeach embodiment may be used alone, or the lubricant base oil accordingto each embodiment may be used in combination with one, or two or moreother base oils. In addition, when the lubricant base oil according toeach embodiment is used in combination with other base oils, a ratio ofthe lubricant base oil of the present invention in the mixed-base oil ispreferably 30% by mass or more, more preferably 50% by mass or more, andfurther preferably 70% by mass or more.

Other base oils used in combination with the lubricant base oilaccording to each embodiment are not particularly limited, and examplesof mineral base oils include solvent refined mineral oils, hydrocrackedmineral oils, hydrorefined mineral oils, and solvent dewaxed base oilshaving a kinematic viscosity at 100° C. of 1 to 100 mm²/s, for example.

Moreover, examples of synthetic base oils include poly-α-olefins orhydrides thereof, isobutene oligomers or hydrides thereof, isoparaffins,alkylbenzenes, alkylnaphthalenes, diesters (ditridecyl glutarate,di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate,di-2-ethylhexyl sebacate and the like), polyol esters(trimethylolpropane caprylate, trimethylolpropane pelargonate,pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate and thelike), polyoxyalkylene glycols, dialkyldiphenyl ethers, and polyphenylethers, and among them, poly-α-olefins are preferable. Typically,examples of the poly-α-olefins include α-olefin oligomers orco-oligomers having a carbon number of 2 to 32, and preferably 6 to 16(1-octene oligomer, decene oligomer, ethylene-propylene co-oligomer andthe like) and hydrides thereof.

Although a producing method of poly-α-olefins is not particularlylimited, examples thereof include a method in which α-olefin ispolymerized in the presence of a polymerization catalyst such as aFriedel-Crafts catalyst including a complex of aluminum trichloride orboron trifluoride with water, an alcohol (ethanol, propanol, butanol andthe like), a carboxylic acid, or ester.

Furthermore, various additive agents may be blended into the lubricantbase oil according to each embodiment or the mixed-base oil of thelubricant base oil and other lubricant base oils, if necessary. Suchadditive agents are not particularly limited, and arbitrary additiveagents that are conventionally used in the field of lubricant oils canbe blended. Specifically, examples of the lubricant oil additive agentsinclude antioxidants, ashless dispersants, metal-based detergents,extreme pressure agents, antiwear agents, viscosity index improvers,pour-point depressants, friction modifiers, oiliness agents, corrosioninhibitors, rust-preventive agents, demulsifying agents, metaldeactivating agents, seal swelling agents, antifoaming agents, andcoloring agents. These additive agents may be used singly or two or morekinds thereof may be used in combination.

For example, the lubricant base oil according to each embodiment caneffectively exhibit the addition effect of a pour-point depressant.Therefore, when the lubricant base oil according to each embodiment orthe mixed-base oil of the lubricant base oil and other lubricant baseoils contains a pour-point depressant, an excellent low-temperatureviscosity characteristic (MRV viscosity at −40° C. is preferably 20,000mPa·s or less, more preferably 15,000 mPa·s or less, and furtherpreferably 10,000 mPa·s or less) can be achieved. In addition, the MRVviscosity at −40° C. described in the present invention means an MRVviscosity at −40° C. measured in conformity with JPI-5S-42-93.

Further, when a pour-point depressant is blended into the lubricant baseoil according to the first embodiment or the lubricant base oilaccording to the second embodiment, the MRV viscosity at −40° C. can be12,000 mPa·s or less, and a lubricant oil composition having anextremely excellent low-temperature viscosity characteristic of morepreferably 10,000 mPa·s or less, further preferably 8,000 mPa·s, andparticularly preferably 6,500 mPa·s or less can be obtained. In thiscase, the amount of the pour-point depressant blended is, on the basisof the total amount of the composition, 0.05 to 2% by mass, andpreferably 0.1 to 1.5% by mass, in particular, in terms of capable ofdecreasing the MRV viscosity, the range of 0.15 to 0.8% by mass is thebest, as the pour-point depressant, one having the weight-averagemolecular weight of preferably 10,000 to 300,000, and more preferably50,000 to 200,000 is particularly preferable, and moreover, as thepour-point depressant, polymethacrylate-based one is particularlypreferable.

EXAMPLES

Hereinafter, the present invention will be described more specificallybased on examples and comparative examples, but the present invention isnot limited to the following examples.

Examples 1-1 to 1-3, Comparative Examples 1-1 and 1-2

In Examples 1-1 to 1-3 and Comparative Examples 1-1 and 1-2, lubricantbase oils shown in Table 1 were each prepared. The lubricant base oilsin Examples 1-1 to 1-3 are obtained based on the method for producing alubricant base oil according to the above-described fourth embodiment.In contrast, the lubricant base oils in Comparative Examples 1-1 and 1-2are obtained by the conventional method for producing a lubricant baseoil. Various characteristics of the respective base oils, and thetraction coefficients measured under conditions of a load of 50 N(average hertz pressure 0.60 GPa), a sample oil temperature of 50° C., acircumferential velocity of 1 m/s, and a slip ratio of 3%, and using a27.4 mm steel ball and a steel disc are shown in Table 1.

TABLE 1 Comp. Comp. Raw materials Example 1-1 Example 1-2 Example 1-3Example 1-1 Example 1-2 General physical properties Density, g/cm³0.8182 0.8181 0.8083 0.8180 0.8184 Flash point, ° C. 232 234 228 238 220Kinematic viscosity, 16.6 17.0 17.1 16.9 17.0 mm²/s (40° C.) (100° C.)4.09 4.13 4.10 4.16 4.10 Viscosity index 154 151 146 157 141 Pour point,° C. −5 −12.5 −17.5 −2.5 −25 Freezing point, ° C. −5 −15 −20 −4 −26NOACK, mass % (250° C.) 11.5 12.0 12.8 12.2 11.8 Sulfur content, massppm <1 <1 <1 <1 <1 Chromatography analysis Saturated content, mass %99.4 99.3 99.5 99.4 99.6 Resin content, mass % 0.4 0.3 0.2 0.4 0.2Aromatic content, mass % 0.2 0.4 0.3 0.3 0.2 Recovery rate, mass % 100100 100 100 100 Urea adduct Adduct amount, mass % 3.18 2.72 2.08 4.051.15 Low-temperature characteristics CCS viscosity (−30° C.), mPa · s870 880 630 990 141 (−35° C.), mP · s 1,650 1,600 1,590 1,950 1,530 SBVviscosity (−20° C.), mPa · s 57,600 12,000 3,200 62,000 810 (−30° C.),mPa · s 478,000 156,000 51,000 880,000 3,370 (−35° C.), mPa · s 783,000492,000 118,000 >1,000,000 9,150 ¹³C-NMR CH 6.6 6.8 7.2 6.4 7.4 CH2 79.178.8 78.3 79.5 78.1 CH3 14.3 14.4 14.5 14.1 14.5 CH2 main chain 19.818.6 15.2 22.0 14.7 EI-MS Paraffins 92.2 92.3 92.1 92.0 92.8 Monocycliccycloparaffin 3.8 4.5 4.2 4.6 4.0 Bicyclic cycloparaffin 3.1 2.3 2.7 2.32.5 Tricyclic cycloparaffin 0.3 0.2 0.1 0.3 0.2 Tetracycliccycloparaffin 0.0 0.0 0.0 0.2 0.0 Pentacyclic cycloparaffin 0.2 0.1 0.10.0 0.1 Hexacyclic cycloparaffin 0.4 0.6 0.5 0.6 0.4 Alkylbenzenes 0.00.0 0.0 0.0 0.0 FD-MS Paraffins 61.1 58.1 50.2 65.3 65.2 Monocycliccycloparaffin 31.4 34.6 39.9 28.5 29.2 Bicyclic cycloparaffin 6.3 6.67.1 5.5 4.4 Tricyclic cycloparaffin 0.5 0.6 2.3 0.4 0.4 Tetracycliccycloparaffin 0.3 0.0 0.2 0.0 0.0 Pentacyclic cycloparaffin 0.1 0.0 0.00.0 0.0 Hexacyclic cycloparaffin 0.3 0.1 0.3 0.3 0.8 Tractioncoefficient 50N, 50° C., 1 m/s, Slip ratio 3% 0.012 0.013 0.015 0.0110.018

Examples 1-4 to 1-9, Comparative Examples 1-3 to 1-5

In Examples 1-4, 1-6, and 1-8, and Comparative Examples 1-3 and 1-5, thelubricant base oils of Examples 1-1 to 1-3, or Comparative Examples 1-1and 1-2, respectively, were used as a sample oil. Furthermore, inExamples 1-5, 1-7, and 1-9, and Comparative Examples 1-4 and 1-6,lubricant oil compositions were prepared by adding 10% by mass of apackage additive (breakdown: 40% by mass of ashless dispersant, 40% bymass of metal-based detergent, 10% by mass of antiwear agent, 8% by massof antioxidant, and 2% by mass of metal deactivating agent) and 5% bymass of a viscosity index improver (polymethacrylate-based, Mw 350,000,effective concentration 50%) to the respective lubricant base oils ofExamples 1-1 to 1-3 or Comparative Examples 1-1 and 1-2, respectively,to be used as a sample oil. Moreover, as Comparative Example 1-7, acommercial 0W-20 oil was prepared. The kinematic viscosities and theviscosity indexes of the respective lubricant oil compositions are shownin Table 2.

[Oil Leakage Test]

With respect to the sample oils of Examples 1-4 to 1-9, and ComparativeExamples 1-3 to 1-6, an oil leakage test was per according to thefollowing procedure.

100 ml of the sample oil is charged in a 200 ml autoclave and an NBRpacking is used to be assembled with a tightening torque of 250 N·musing a torque wrench. A two-way cock is used at the upper part and, asa sealing material, a teflon (registered trademark) packing is used tobe assembled with a tightening torque of 250 N·m using a torque wrench.After assembling, a pressure is increased to 200 kPa with nitrogen gas.The respective sample oils are subjected to the same operation and areset upside down in a low-temperature thermostat bath that is controlledto be −30±1 C°. Results are evaluated by oil leakage from the NBRpacking after 48 hours, and with leakage is evaluated as presence andwithout leakage is evaluated as absence.

The obtained results are shown in Tables 2 and 3.

[JC08 Hot Mode Fuel Consumption Evaluation Test]

With respect to the lubricant oil compositions of Examples 1-5, 1-7, and1-9, and Comparative Examples 1-4 and 1-6, a JC08 hot mode fuelconsumption evaluation test was performed according to the followingprocedure.

JC08 mode is a method for measuring fuel consumption of vehicles,established by Ministry of Land, Infrastructure, Transport and Tourism(for details, refer to Ministry of Land, Infrastructure, Transport andTourism, Announcement that Prescribes Details of Safety Standards forRoad Trucking Vehicles [2009 Jul. 30] Attachment 42 Measurement Methodof Exhaust Gas of Light and Middle Vehicles). JC08 is classified into acold mode that starts in an engine cold state and a hot mode thatmeasures fuel consumption in an engine warm state. In the test, a 2.5 L,FF gasoline engine vehicle (Toyota ESTIMA) was selected, the engine waswashed and filled with a newly-prepared sample oil before the start ofthe test, the test vehicle was made to warm up at a constant rate of60±2 km/h for 15 minutes or more on a chassis dynamometer, and then, wasquickly returned to the idling state, the vehicle was driven in apredetermined running pattern, and consumed fuel was calculated fromexhaust gas to determine fuel consumption. The obtained results areshown in Tables 2 and 3.

TABLE 2 Example Example Example Example Example Example 1-4 1-5 1-6 1-71-8 1-9 Base Kind Example 1 Example 1 Example 2 Example 2 Example 3Example 3 oil Content (% by mass) 100 Balance 100 Balance BalanceBalance Package additive (% by mass) — 10 — 10 — 10 Viscosity indeximprover — 5 — 5 — 5 (% by mass) Characteristics of sample oil (0W-20)Kinematic viscosity, mm²/s (100° C.) 4.09 8.19 4.13 8.22 4.10 8.18Viscosity index 154 244 151 240 146 242 SBV viscosity (mPa · s) −20° C.57,600 59,000 3,200 3,450 3,200 3,380 −30° C. 478,000 520,000 51,00053,000 51,000 52,000 Oil leakage test (−20° C.) Absence Absence AbsenceAbsence Absence Absence Presence or absence of leakage JC08 hot modefuel consumption — 1.85 — 1.71 — 1.52 Fuel consumption improving ratio,%

TABLE 3 Comp. Comp. Comp. Comp. Comp. Example 1-3 Example 1-4 Example1-5 Example 1-6 Example 1-7 Base oil Kind Comp. Comp. Comp. Comp.Commercial Example 1 Example 1 Example 2 Example 2 0W-20 oil Content(mass %) 100 Balance 100 Balance Package additive (mass %) — 10 — 10Viscosity index improver (mass %) — 5 — 5 Characteristics of sample oil(0W-20) Kinematic viscosity, mm²/s (100° C.) 4.16 8.28 4.04 8.33 8.42viscosity index 157 245 141 237 230 SBV viscosity (mPa · s) −20° C.62,000 68,000 810 3,500 — −30° C. 880,000 >1,000,000 3,370 4,800 — Oilleakage test (−20° C.) Absence Absence Presence Presence — Presence orabsence of leakage JC08 hot mode fuel consumption — 0.11 — 0.05 — Fuelconsumption improving ratio, %

Examples 2-1 and 2-2, Comparative Examples 2-1 to 2-3

In Examples 2-1 and 2-2 and Comparative Examples 2-1 to 2-3, lubricantbase oils shown in Table 4 were each prepared. The lubricant base oilsin Examples 2-1 and 2-2 are obtained based on the method for producing alubricant base oil according to the above-described fourth embodiment.In contrast, the lubricant base oils in Comparative Examples 2-1 to 2-3are obtained by the conventional method for producing a lubricant baseoil. Various characteristics of the respective base oils, and thetraction coefficients measured under conditions of a load of 50 N(average hertz pressure 0.60 GPa), a sample oil temperature of 50° C., acircumferential velocity of 1 m/s, and a slip ratio of 3%, and using a27.4 mm steel ball and a steel disc are shown in Table 4.

TABLE 4 Comp. Comp. Comp. Raw materials Example 2-1 Example 2-2 Example2-1 Example 2-2 Example 2-3 General physical properties Density, g/cm³0.8273 0.8272 0.8270 0.8260 0.8288 Flash point, ° C. 262 260 264 250 254Kinematic viscosity, 30.3 28.2 29.4 26.0 30.8 mm²/s (40° C.) (100° C.)6.30 5.92 6.20 5.48 6.07 Viscosity index 165 162 167 154 148 Pour point,° C. −5 −12.5 −2.5 −15 −30 Freezing point, ° C. −5 −14 −4 −17 −32 Sulfurcontent, mass ppm <1 <1 <1 <1 <1 Chromatography analysis Saturatedcontent, mass % 99.2 99.2 99.3 99.5 99.4 Resin content mass % 0.4 0.30.3 0.2 0.2 Aromatic content, mass % 0.4 0.5 0.4 0.3 0.4 Recovery rate,mass % 100 100 100 100 100 Urea adduct Adduct amount, mass % 1.25 0.772.33 0.11 0.13 Low-temperature characteristics CCS viscosity (−30° C.),mPa · s 790 880 1,070 995 1,020 (−35° C.), mP · s 1,210 1,320 1,7801,625 1,850 SBV viscosity (−20° C.), mP · s 29,000 3,200 122,000 2,1001,030 (−25° C.), mP · s 470,000 5,300 >1,000,000 4,300 1,700 ¹³C-NMR CH6.2 6.5 6.0 7.1 6.8 CH2 82.0 81.5 83.2 79.8 80.0 CH3 11.2 12.0 10.8 13.113.2 CH2 main chain 25.3 20.3 25.9 18.0 16.0 EI-MS Paraffins 81.2 80.182.6 83.2 80.0 Monocyclic cycloparaffin 12.9 13.4 11.8 11.0 12.7Bicyclic cycloparaffin 4.8 5.0 3.9 4.3 5.3 Tricyclic cycloparaffin 0.91.0 0.8 0.6 1.1 Tetracyclic cycloparaffin 0.1 0.1 0.1 0.1 0.2Pentacyclic cycloparaffin 0.0 0.0 0.2 0.2 0.2 Hexacyclic cycloparaffin0.1 0.4 0.6 0.6 0.5 Alkylbenzenes 0.0 0.0 0.0 0.0 0.0 FD-MS Paraffins36.8 39.7 35.9 47.2 49.4 Monocyclic cycloparaffin 46.9 44.1 47.2 41.239.5 Bicyclic cycloparaffin 13.8 13.0 14.1 9.7 8.7 Tricycliccycloparaffin 2.1 2.4 2.2 1.4 1.2 Tetracyclic cycloparaffin 0.1 0.2 0.20.1 0.1 Pentacyclic cycloparaffin 0.0 0.0 0.0 0.1 0.2 Hexacycliccycloparaffin 0.3 0.6 0.4 0.3 0.9 Traction coefficient 50N, 25° C., 0.5m/s, Slip ratio 3% 0.017 0.016 0.014 0.018 0.022

Examples 2-3 to 2-6, Comparative Examples 2-4 to 2-9

In Examples 2-3 and 2-5, and Comparative Examples 2-4, 2-6, and 2-8, thelubricant base oils of Examples 2-1 and 2-2, or Comparative Examples 2-1to 2-3, respectively, were used as a sample oil. Furthermore, inExamples 2-4, 2-6, and Comparative Examples 2-5; 2-7, and 2-9, lubricantoil compositions were prepared by adding 0.8 mass % of a packageadditive (breakdown: 60 mass % of antiwear agent, 25 mass % ofantioxidant, 10 mass % of rust inhibitor, and 5 mass % of metaldeactivating agent) to the respective lubricant base oils of Examples2-1 and 2-2, or Comparative Examples 2-1 to 2-3, respectively, to beused as a sample oil.

[Oil Leakage Test]

With respect to the sample oils of Examples 2-3 to 2-6, and ComparativeExamples 2-4 to 2-9, an oil leakage test was performed according to thefollowing procedure.

100 ml of the sample oil is charged in a 200 ml autoclave and an NBRpacking is used to be assembled with a tightening torque of 250 N·musing a torque wrench. A two-way cock is used at the upper part and, asa sealing material, a teflon (registered trademark) packing is used tobe assembled with a tightening torque of 250 N·m using a torque wrench.After assembling, a pressure is increased to 300 kPa with nitrogen gas.The respective sample oils are subjected to the same operation and areset upside down in a low-temperature thermostat bath that is controlledto be −30±1 C°. Results are evaluated by oil leakage from the NBRpacking after 48 hours, and with leakage is evaluated as presence andwithout leakage is evaluated as absence.

The obtained results are shown in Tables 5 and 6.

[Storage Stability Test]

With respect to the sample oils of Examples 2-3 to 2-6, and ComparativeExamples 2-4 to 2-9, a storage stability test was performed according tothe following procedure.

In a 100 ml screw vial, an oil is charged to two thirds or more thereof,and each of the test tube is put in a refrigerator of 0±1° C., and theappearance is confirmed after 48 hours. Without change in the appearanceis evaluated as without change, and generation of condensation isevaluated as condensation.

[Energy Saving Property Evaluation Test]

With respect to the lubricant oil compositions of Examples 2-4 and 2-6,and Comparative Examples 2-5, 2-7, and 2-9, an energy saving propertyevaluation test was performed according to the following procedure.

The energy saving property was evaluated by using a compact hydraulicunit. A variable capacity piston pump was used for a pump in the compacthydraulic unit, the oil amount was 15 L, the oil temperature was 80±2°C. and 0° C. that considers the time of low-temperature starting, andthe input power of a motor when the discharge pressure is varied from0.8 to 2.4 MPa using a commercial hydraulic oil (0W-20, kinematicviscosity at 40° C.: 32.8 mm²/s, viscosity index: 125) was measured.Next, the input power of a motor was measured by using each of thelubricant oil compositions of Examples 3, 4 and Comparative Examples 4to 6 as a sample oil, and the energy saving property was evaluated basedon a difference of power consumption from a sample oil of ComparativeExample 7.

The obtained results are shown in Tables 5 and 6.

TABLE 5 Example 2-3 Example 2-4 Example 2-5 Example 2-6 Base KindExample 2-1 Example 2-1 Example 2-2 Example 2-2 oil Content 100 Balance100 Balance (mass %) Package additive (mass %) — 0.8 — 0.8Characteristics of sample oil Kinematic viscosity. mm²/_(s) 30.3 30.528.2 28.4 (40° C.) Viscosity index 165 164 162 162 SBV viscosity (mPa ·s) −20° C. 29,000 29,500 3,200 3,300 −30° C. 470,000 490,000 5,300 5,500Oil leakage test (−20° C.) Absence Absence Absence Absence Presence orabsence of leakage Storage stability (0° C.) Without Without Withoutwithout change change change change Energy saving property 80° C. — +6.5— +4.9  0° C. — +3.5 — +3.1

TABLE 6 Comp. Comp. Comp. Comp. Comp. Comp. Example Example ExampleExample Example 2-4 Example 2-5 2-6 2-7 2-8 2-9 Base Kind Comp. Comp.Comp. Comp. Comp. Comp. oil Example 2-1 Example 2-1 Example ExampleExample Example 2-2 2-2 2-3 2-3 Content (mass %) 100 Balance 100 Balance100 Balance Package additive (mass %) — 0.8 — 0.8 — 0.8 Characteristicsof sample oil Kinematic viscosity. mm²/s 29.4 29.7 26.0 26.3 30.8 31.0(40° C.) Viscosity index 167 166 154 152 148 146 SBV viscosity (mPa · s)−20° C. 122,000 123,000 2,100 2,300 1,030 1,100 −30°C. >1,000,000 >1,000,000 4,300 4,500 1,700 1.800 Oil leakage test (−20°C.) Absence Absence Presence Presence Presence Presence Presence orabsence of leakage Storage stability test (0° C.) CondensationCondensation Without Without Without Without change change change changeEnergy saving property  80° C. — +6.2 — +0.6 — +0.8  0° C. — −0.3 — +1.4— +1.2

Examples 3-1 to 3-3, Comparative Examples 3-1 to 3-3

In Examples 3-1 to 3-3 and Comparative Examples 3-1 to 3-3, lubricantbase oils shown in Table 7 were each prepared. The lubricant base oilsin Examples 3-1 to 3-3 are obtained based on the method for producing alubricant base oil according to the above-described fourth embodiment.In contrast, the lubricant base oils in Comparative Examples 3-1 to 3-3are obtained by the conventional method for producing a lubricant baseoil. Various characteristics of the respective base oils, and thetraction coefficients measured under conditions of a load of 50 N(average hertz pressure 0.60 GPa), a sample oil temperature of 50° C., acircumferential velocity of 1 m/s, and a slip ratio of 3%, and using a27.4 mm steel ball and a steel disc are shown in Table 7.

TABLE 7 Example Example Example Comp. Comp. Comp. 3-1 3-2 3-3 Example3-1 Example 3-2 Example 3-3 General physical properties Density, g/cm³0.8054 0.8055 0.8056 0.8057 0.8058 — Flash point, ° C. 204 202 200 205197 — Kinematic viscosity, mm²/s (40° C.) 9.23 8.10 9.16 9.19 9.22 8.48(100° C.) 2.70 2.45 2.66 2.70 2.65 2.51 Viscosity index 138 133 131 140129 127 Pour point, ° C. −11 −22.5 −27.5 −7.5 −30 −40 Freezing point, °C. −15 −24 −28 −8 −31 −43 NOACK, mass % (250° C.) 44.8 46.2 48.6 52.856.2 55.1 Sulfur content, mass ppm <10 <10 <10 <10 <10 <10 Iodine value0.08 0.07 0.08 0.07 0.09 0.07 Aniline point, ° C. 111.1 110.6 110.7112.5 111.8 112.0 Chromatography analysis Saturated content, mass % 99.699.4 99.5 99.6 99.6 99.3 Resin content, mass % 0.3 0.3 0.3 0.2 0.2 0.3Aromatic content, mass % 0.1 0.3 0.2 0.2 0.2 0.4 Recovery rate, mass %100 100 100 100 100 100 Urea adduct amount, mass % 9.68 4.25 4.02 12.50.58 0.11 nP, mass % 15.2 23.9 22.2 14.8 32.8 37.5 nP Base oilconversion amount, 1.47 1.02 0.89 1.85 0.19 0.04 mass % Low-temperaturecharacteristics SBV viscosity, mP · s (−20° C.) 1,500 100 110 4,500 130<1000 (−25° C.) 3,100 430 240 37,000 200 — (−30° C.) 19,200 2,120 1,05049,000 780 270 (−35° C.) 290,000 13,300 3,300 900,000 1,970 1,040 (−40°C.) 720,000 29,000 5,300 >1,000,000 3,830 2,110 ¹³C-NMR CH 7.6 7.8 7.77.4 7.7 7.6 CH2 76.4 76.1 75.9 76.6 76.0 75.6 CH3 16.0 16.1 16.2 16.016.3 16.8 CH2 main chain 16.9 16.4 15.1 17.1 13.3 10.1 EI-MS Paraffins98.2 98.1 97.9 98.3 98.0 97.7 Monocyclic cycloparaffin 0.0 0.0 0.0 0.00.0 0.0 Bicyclic cycloparaffin 1.3 1.5 1.4 1.5 1.7 1.7 Tricycliccycloparaffin 0.3 0.4 0.3 0.1 0.3 0.3 Tetracyclic cycloparaffin 0.1 0.00.2 0.0 0.0 0.0 Pentacyclic cycloparaffin 0.0 0.0 0.0 0.1 0.0 0.0Hexacyclic cycloparaffin 0.1 0.0 0.2 0.0 0.0 0.3 Alkylbenzenes 0.0 0.00.0 0.0 0.0 0.0 FD-MS Paraffins 79.9 76.2 70.4 82.1 68.5 67.9 Monocycliccycloparaffin 18.5 20.1 25.8 16.3 26.4 27.3 Bicyclic cycloparaffin 1.22.9 3.0 1.1 4.0 4.1 Tricyclic cycloparaffin 0.2 0.3 0.5 0.3 0.5 0.4Tencyclic cycloparaffin 0.0 0.0 0.0 0.0 0.0 0.0 Pentacycliccycloparaffin 0.1 0.0 0.1 0.0 0.1 0.0 Hexacyclic cycloparaffin 0.1 0.50.2 0.2 0.5 0.3 Traction coefficient 0.013 0.014 0.015 0.011 0.016 0.019

Examples 3-4 to 3-6, Comparative Examples 3-4 to 3-6

In Examples 3-4 to 3-6 and Comparative Examples 3-4 to 3-6, lubricantoil compositions were prepared by adding 8% by mass of a packageadditive (breakdown: antiwear agent: 12% by mass, ashless dispersant:50% by mass, pour-point depressant: 1% by mass, antioxidant: 12% bymass, metal-based detergent: 25% by mass) and 5% by mass of a viscosityindex improver (polymethacrylate-based, Mw 350,000, effectiveconcentration 50% by mass) to the lubricant base oils of Examples 3-4 to3-6 and Comparative Examples 3-4 to 3-6, respectively.

[Oil Leakage Test]

With respect to the sample oils of Examples 3-4 to 3-9, and ComparativeExamples 3-4 to 3-9, an oil leakage test was performed according to thefollowing procedure.

More specifically, as a low-temperature leakage test, an actualtransmission was used, the sample oil was encapsulated in thetransmission to be stored at low temperature, and oil leakage (bleed)was evaluated. The obtained results are shown in Tables 8 and 9.

[Storage Stability Test]

With respect to the sample oils of Examples 3-4 to 3-9, and ComparativeExamples 3-4 to 3-9, a storage stability test was performed according tothe following procedure.

In a 100 ml screw vial, an oil is charged to two thirds or more thereof,and each of the test tube is put in a refrigerator of 0±1° C., and theappearance is confirmed after 48 hours. Without change in the appearanceis evaluated as without change, and generation of condensation isevaluated as condensation.

[Low-Temperature Roller Bearing Test]

With respect to the lubricant oils of Examples 3-4, 3-6, and 3-8, andComparative Examples 3-4, 3-6, and 3-8, a low-temperature roller bearingtest was performed using a high-pressure friction tester. Morespecifically, a measurement site is cooled to 0° C. by a cooling jacketunder the ordinary pressure condition and the temperature is kept for 4hours. A cylindrical roller bearing was used as a test piece, and afriction coefficient was evaluated. The obtained results are shown inTables 8 and 9. The smaller friction coefficient in Table 7 means anexcellent reduction in the friction coefficient at the beginning ofrolling, in particular, and has a correlation with cold startability bya real machine.

TABLE 8 Example Example Example Example Example Example 3-4 3-5 3-6 3-73-8 3-9 Base Kind Example Example Example Example Example Example oil3-1 3-1 3-2 3-2 3-3 3-3 Content 100 Balance 100 Balance Balance Balance(mass %) Package additive (mass %) — 8 — 8 — 8 Viscosity index improver— 5 — 5 — 5 (mass %) SBV viscosity mPa · s 720,000 320.000 29,000 16,0005,300 5,500 −40° C. Oil leakage test (−30° C.) Absence Absence AbsenceAbsence Absence Absence Presence or absence of leakage Low-temperaturestorage Without Without Without Without Without Without stability changechange change change change change Low-temperature roller 0.020 — 0.021— 0.022 — bearing test Friction coefficient

TABLE 9 Comp. Comp. Comp. Comp. Comp. Comp. Example Example ExampleExample Example Example 3-4 3-5 3-6 3-7 3-8 3-9 Base Kind Comp. Comp.Comp. Comp. Comp. Comp. oil Example Example Example Example ExampleExample 3-1 3-1 3-2 3-2 3-3 3-3 Content 100 Balance 100 Balance BalanceBalance (mass %) Package additive (mass %) — 8 — 8 — 8 Viscosity indeximprover — 5 — 5 — 5 (mass %) SBV viscosity mPa · s >1,000,000 560,0003,830 4,200 2,110 1,980 −40° C. Oil leakage test (−30° C.) AbsenceAbsence Presence Presence Presence Presence Presence or absence ofleakage Low-temperature storage Condensation Condensation WithoutWithout Without Without stability change change change changeLow-temperature roller 0.052 — 0.028 — 0.030 — bearing test frictioncoefficient

1. A lubricant base oil that is a hydrocarbon oil that satisfies any ofthe following conditions (i), (ii) and (iii): (i) a hydrocarbon oilhaving a kinematic viscosity at 100° C. of 3.0 to 5.0 mm²/s, a viscosityindex of 145 or more, and an SBV viscosity at −20° C. of 3,000 to 60,000mPa·s, (ii) a hydrocarbon oil having a kinematic viscosity at 100° C. of5 to 9 mm²/s, a viscosity index of 155 or more, and an SBV viscosity at−20° C. of 3,000 to 30,000 mPa·s, and (iii) a hydrocarbon oil having akinematic viscosity at 100° C. of 2.0 to 3.0 mm²/s, a viscosity index of130 or more, and an SBV viscosity at −30° C. of 1,000 to 30,000 mPa·s.2. The lubricant base oil according to claim 1, wherein the hydrocarbonoil satisfies the condition (i) and has an SBV viscosity at −30° C. of5,000 to 500,000 mPa·s.
 3. The lubricant base oil according to claim 1,wherein the hydrocarbon oil satisfies the condition (i) and has afreezing point of −20 to −5° C.
 4. The lubricant base oil according toclaim 1, wherein the hydrocarbon oil satisfies the condition (i) and hasa ratio of CH₂ carbons constituting a main chain to all carbonsconstituting the lubricant base oil of 15% or more in a ¹³C-NMRanalysis.
 5. The lubricant base oil according to claim 1, wherein thehydrocarbon oil satisfies the condition (i) and has a cycloparaffincontent of 50% or less in an FD-MS analysis.
 6. The lubricant base oilaccording to claim 1, wherein the hydrocarbon oil satisfies thecondition (ii) and has an SBV viscosity at −25° C. of 5,000 to 500,000mPa·s.
 7. The lubricant base oil according to claim 1, wherein thehydrocarbon oil satisfies the condition (ii) and has a freezing point of−15 to −5° C.
 8. The lubricant base oil according to claim 1, whereinthe hydrocarbon oil satisfies the condition (ii) and has a ratio of CH₂carbons constituting a main chain to all carbons constituting thelubricant base oil of 20% or more in a ¹³C-NMR analysis.
 9. Thelubricant base oil according to claim 1, wherein the hydrocarbon oilsatisfies the condition (ii) and has a cycloparaffin content of 60% orless in an FD-MS analysis.
 10. The lubricant base oil according to claim1, wherein the hydrocarbon oil satisfies the condition (iii) and has anSBV viscosity at −35° C. of 3,000 to 500,000 mPa·s.
 11. The lubricantbase oil according to claim 1, wherein the hydrocarbon oil satisfies thecondition (iii) and has a freezing point of −30 to −10° C.
 12. Thelubricant base oil according to claim 1, wherein the hydrocarbon oilsatisfies the condition (iii) and has a ratio of CH₂ carbonsconstituting a main chain to all carbons constituting the lubricant baseoil of 15% or more in a ¹³C-NMR analysis.
 13. The lubricant base oilaccording to claim 1, wherein the hydrocarbon oil satisfies thecondition (iii) and has a cycloparaffin content of 30% or less in anFD-MS analysis.
 14. A method for producing a lubricant base oil, themethod comprising: a first step of fractionating, from a hydrocarbon oilcontaining a base oil fraction and a heavy fraction that is heavier thanthe base oil fraction, the base oil fraction and the heavy fraction; asecond step of returning a cracked oil obtained by hydrocracking theheavy fraction fractionated in the first step, to the first step; athird step of obtaining a dewaxed oil by performing hydroisomerizationdewaxing of the base oil fraction; a fourth step of obtaining a refinedoil by refining the dewaxed oil; and a fifth step of obtaining alubricant base oil that is a hydrocarbon oil that satisfies any of thefollowing conditions (i), (ii) and (iii): (i) a hydrocarbon oil having akinematic viscosity at 100° C. of 3.0 to 5.0 mm²/s, a viscosity index of145 or more, and an SBV viscosity at −20° C. of 3,000 to 60,000 mPa·s,(ii) a hydrocarbon oil having a kinematic viscosity at 100° C. of 5 to 9mm²/s, a viscosity index of 155 or more, and an SBV viscosity at −20° C.of 3,000 to 30,000 mPa·s, and (iii) a hydrocarbon oil having a kinematicviscosity at 100° C. of 2.0 to 3.0 mm²/s, a viscosity index of 130 ormore, and an SBV viscosity at −30° C. of 1,000 to 30,000 mPa·s, byfractionation of the refined oil.
 15. The method according to claim 14,wherein the lubricant base oil obtained in the fifth step satisfies thecondition (i) and has a freezing point of −20 to −5° C.
 16. The methodaccording to claim 14, wherein the lubricant base oil obtained in thefifth step satisfies the condition (ii) and has a freezing point of −15to −5° C.
 17. The method according to claim 14, wherein the lubricantbase oil obtained in the fifth step satisfies the condition (iii) andhas a freezing point of −30 to −10° C.
 18. The method according to claim14, wherein the third step is a step of performing hydroisomerizationdewaxing of the base oil fraction in the presence of ahydroisomerization catalyst containing at least one crystalline solidacidic substance selected from the group consisting of ZSM-22-typezeolite, ZSM-23-type zeolite, SSZ-32-type zeolite, and ZSM-48-typezeolite and platinum and/or palladium as an active metal.
 19. The methodaccording to claim 14, wherein the hydrocarbon oil is obtained by usingGTL wax obtained by a Fischer-Tropsch synthesis or slack wax obtained bysolvent dewaxing, as a raw material.